tag:blogger.com,1999:blog-79398368294416414272024-03-05T18:01:44.037+02:00Greens and StarsAre there such things as birdie putts and dark skies? I intend to find out.Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.comBlogger248125tag:blogger.com,1999:blog-7939836829441641427.post-83495928956586535072017-02-22T14:34:00.000+02:002017-02-22T14:43:14.260+02:00Exploring data with Visual Studio Code<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiSHbtt7O9eG5HJ0QKoIY8Y5j5IaCaTfSs6lyu1luzdSJjQlrashbmP1iA5FtaiT65t4cUZyZbOJGVEF5YaTWeNcYO2lzs0fqdWykm1KvLP96T6Pabd8kk3o_ZVGnVonwnIfYjHRk_10KU/s1600/bokeh-1.png" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="268" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiSHbtt7O9eG5HJ0QKoIY8Y5j5IaCaTfSs6lyu1luzdSJjQlrashbmP1iA5FtaiT65t4cUZyZbOJGVEF5YaTWeNcYO2lzs0fqdWykm1KvLP96T6Pabd8kk3o_ZVGnVonwnIfYjHRk_10KU/s320/bokeh-1.png" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig 1: Visual presentation of Radix sort steps</td></tr>
</tbody></table>
Every now and then I have a need to visualize some data, be it spectral spread of stars in a cluster, a spurious correlation or a stream of measurements. I've always used whatever happens to be handy and available, often kludging data from format to another and using Excel or Python+matplotlib to create the visuals. Both have repeatedly left me wanting on either appearance or ease of updating.<br />
<br />
Enter Visual Studio Code to the equation. A small, nimble editor with interesting extensions: Python with support for Jupyter notebooks and Bokeh chart library. And the best part is, <a href="https://notebooks.azure.com/" rel="nofollow" target="_blank">Python and Jupyter notebooks are first class citizens in the big data cloud services</a>. So I should be able to take my existing code, update data reading parts to read my data points from cloud storage and I'd be ready to marvel a beautiful visualization of said data in my browser.<br />
<br />
<h3>
Installing tools</h3>
To start on the journey, you need to install a few things. To start, install <a href="https://code.visualstudio.com/" rel="nofollow" target="_blank">Visual Studio Code</a> first. And you need to install Python, I recommend <a href="https://www.python.org/downloads/release/python-360/" rel="nofollow" target="_blank">3.6.0</a> and the libraries for number crunching and visualization. You can use <a href="https://docs.python.org/3/installing/" rel="nofollow" target="_blank">PIP </a>for that on command line, i.e. use either <span style="font-family: "courier new" , "courier" , monospace;">pip install <package_name> </span>or <span style="font-family: "courier new" , "courier" , monospace;">python -m pip install <package_name></span><br />
<br />
Python Packages you need are:<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjIBsBX9eEsINZzE4P5gsTza_On-HQEtThFRMiu6TjGcNddzlFXA2tZH2qIhi7mwhPfeWkiU36Fml7gwagDED4C5tj5p40SOafeDCaz-e0enL9bdkZUGezFmtvERDQvRgKV7lOhszZ23eM/s1600/vsc-python-ext.png" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="232" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjIBsBX9eEsINZzE4P5gsTza_On-HQEtThFRMiu6TjGcNddzlFXA2tZH2qIhi7mwhPfeWkiU36Fml7gwagDED4C5tj5p40SOafeDCaz-e0enL9bdkZUGezFmtvERDQvRgKV7lOhszZ23eM/s320/vsc-python-ext.png" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig 2: Visual Studio Code extension for python</td></tr>
</tbody></table>
<ul>
<li>numpy</li>
<li>scipy</li>
<li>bokeh</li>
<li>jupyter</li>
<li>ipython</li>
<li>pylint</li>
</ul>
Optional but nice to have libraries are:<br />
<ul>
<li>matplotlib</li>
<li>pandas</li>
</ul>
<div>
Some libraries might be included already as dependencies of the others. Now you are almost ready to go, so start up VSCode and go to the extensions tab and search for "Python" (see Fig 2). Install and reload the VSCode window.</div>
<div>
<br /></div>
<h3>
First chart</h3>
<div>
To test everything works, you need a simple test case, how about a simple parabolic curve?<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyGxQYx63_oex_eTAKORPOd9GhOdG33S3TJYjQjm7wCEVO61bAuwlxWtPwlIQ-zHVfcaMI-uFknlUaiIvA9Z0Rumd3fesIC3l3xU9w8wpaac0_mi6CkSxgqK6v2nvpvmatbNq98M3cKz0/s1600/curve-1.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="166" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyGxQYx63_oex_eTAKORPOd9GhOdG33S3TJYjQjm7wCEVO61bAuwlxWtPwlIQ-zHVfcaMI-uFknlUaiIvA9Z0Rumd3fesIC3l3xU9w8wpaac0_mi6CkSxgqK6v2nvpvmatbNq98M3cKz0/s320/curve-1.png" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig 3: Code and output for a simple chart</td></tr>
</tbody></table>
</div>
<div>
<script src="https://gist.github.com/mickut/12217aa7372732fd8dc5927cd1df42de.js"></script>
</div>
<div>
<br /></div>
<div>
So, what's going on there? The line 2 contains a IPython notebook cell separator, you can use these to mark executable cells for your notebook, and click on the "Run cell" button above marker to execute the following block of code. Read more on a <a href="https://donjayamanne.github.io/pythonVSCodeDocs/docs/jupyter_getting-started/" rel="nofollow" target="_blank">Jupyter notebooks on VSCode by the author of the Python extension</a>, Don Jayamanne.<br />
<br />
The lines 3-6 import several Python module, namely Bokeh features for outputting to a notebook, plotting a figure and displaying inline-HTML text.<br />
<br />
The line 8 defines a dictionary of common parameters for our plots, these get used by the kwargs syntax when calling <span style="font-family: "courier new" , "courier" , monospace;">plot()</span>.<br />
<br />
Line 9 defines that our output should be a notebook and it should use inline resources instead of network resources.<br />
<br />
Line 10 creates a sample text output to our notebook.<br />
<br />
Lines 11-13 create a data set and a plot for it.<br />
<br />
Line 14 shows our plot on the notebook.<br />
<br />
Line 15 ensures that the notebook is pushed into VSCode output window.<br />
<br />
<h3>
More charts</h3>
Let's try a bigger sample, showing how a radix sort changes the array in each iteration.<br />
<br /></div>
<div>
<script src="https://gist.github.com/mickut/e39ff37e94c14ef73f0cc4f8f6b6242e.js"></script></div>
<div>
<br />
The output can be seen in Fig 1. This code uses Numpy to create an array of random numbers, then sorts those using an implementation of radix sort in base 16. The interim sorting round arrays are plotted to a single figure using the <span style="font-family: "courier new" , "courier" , monospace;">multi_line</span> -function.<br />
<br />
If you want even more, you can take a look at the <a href="http://bokeh.pydata.org/en/latest/docs/gallery.html" rel="nofollow" target="_blank">Bokeh examples</a>, such as <a href="http://bokeh.pydata.org/en/latest/docs/gallery/heatmap_chart.html" rel="nofollow" target="_blank">Heatmap.py</a> which creates an HTML file with charts and opens it into your browser. A good excercise is to update that code to output into the VSCode window instead.<br />
<br /></div>
<h3>
Issues</h3>
<div>
At least currently there are a few glitches. The Python kernel isn't keen to change the output method of Jupyter notebooks, so if you have multiple windows open with both HTML file and VSCode window output, your HTML files might get corrupted when executing a cell from another file. To get around this, point your mouse to the status row at bottom, click on the "Python 3 kernel" and select "Restart Python 3 kernel" whenever switching between files. I haven't found a direct Shift-Ctrl-P shortcut command for this yet.</div>
<div>
<br /></div>
Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-2956261243257689342015-01-17T14:59:00.002+02:002015-01-17T15:18:49.027+02:00Astrophysics as a side-product<div>
<div style="float: right; margin-bottom: 1em; margin-left: 1em;">
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="https://www.flickr.com/photos/mickut/8621752935" style="margin-bottom: 1em; margin-left: auto; margin-right: auto;" title="Messier 48 by Antti Kuntsi, on Flickr"><img alt="Messier 48" height="252" src="https://farm9.staticflickr.com/8110/8621752935_4eabe92646_n.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">LRGB image of Messier 48 taken in April 2013</td></tr>
</tbody></table>
</div>
I ran across a <a href="http://pixinsight.com/forum/index.php?topic=8010">forum posting on creating Hertzsprung-Russell diagrams</a> from astrophotos using PixInsight. Since PixInsight is my tool of choice for processing astronomical data, I decided to try it out on one of my image stacks.
<br />
The process itself is quite straight forward as described. Once images are calibrated, registered and stacked, you simply generate CSV files from V and B channels (green is close to photometric V) using the FWHMEccentricity script in PI. From my image it found 1266 stars for G and 836 for B.<br />
For reference data on actual magnitude you then solve the image and use AnnotateImage to generate a file containing Tycho catalog data on found stars (found 241).<br />
<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="https://www.flickr.com/photos/mickut/15677006784" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;" title="M48 Hertzsprung–Russell diagram by Antti Kuntsi, on Flickr"><img alt="M48 Hertzsprung–Russell diagram" height="271" src="https://farm9.staticflickr.com/8599/15677006784_837f6216bb_n.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="max-width: 300px; text-align: center;">Hertzsprung-Russell diagram of Messier 48 with 809 stars</td></tr>
</tbody></table>
The three generated files are combined on spreadsheet, the star fluxes are calculated from the FWHM data <br />
<pre>Flux=(A*SizeX*SizeY*Pi/3)</pre>
and all stars on all files get a positional index <br />
<pre>Index= int(X)+int(Y)*ImageWidth</pre>
that is later used to correlate individual stars. If you use Excel, put <tt>Index</tt> into column A. The flux is converted to magnitude scale with
<br />
<pre>mag=-2.5 * Log10(flux)</pre>
<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="https://www.flickr.com/photos/mickut/15677305274" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;" title="M48 HR data linearity by Antti Kuntsi, on Flickr"><img alt="M48 HR data linearity" height="264" src="https://farm8.staticflickr.com/7502/15677305274_6d2a65ee40_n.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="max-width: 300px; text-align: center;">SXVR-H18 CCD linear fit shows anti-bloom gate effect on the brighter stars bottom-left</td></tr>
</tbody></table>
Now we have all the datapoints in compatible numeric spaces, so the calculated magnitudes can be fitted with catalog data using a simple linear regression. In Excel you can use <tt>VLOOKUP</tt> macro to match each star by the calculated <tt>Index</tt> to match the across the three files. Create separate fits for V (or G) and B, and use the fit function to create yet another column for linearized magnitudes. You can also simplify this by simply using the average offset, if your linear fit is very good and the channel fit slopes nearly identical.<br />
<br />
Once you have your calibrated magnitudes from your image data, you can create the final column, "B-V" and use it with V (or G) to create a scatter plot. Put V as the vertical axis and reverse the axis to increase downwards. Clamp the ranges, adjust styles and enjoy your newly generated (pseudo)science. If all goes well, you should be able to see a plot that matches some region of the real star sequence plots. My M48 seems to be a pretty good match on main sequence and sub-giant stars.</div>
Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-43496775417213329762013-09-25T23:49:00.002+03:002013-09-25T23:51:21.215+03:00Update on shutter repairsAfter a serious series of testing the refurbished shutter modules I have learned more. There's another way for the shutter to fail, and it's sneaky. The shutter blades are very thin metal and they very quickly gnaw a bit of play around the slotted axel. There's also some slack on the planetary gear, and as a result the shutter can flop about a minute amount.
The movement is very minimal, but with relatively small tolerance that's enough to cast a shadow on the edge of sensor, or have a tiny gap when closed. I wouldn't have noticed this less I had held the assembled camera in hand and looked in with the camera at
the right angle.
I tried a range of glues, but those didn't hold on the blade and tiny axel at all. I was running out of options when I realized the play isn't an issue, all I have to do is make sure the blades don't flail around out of position. The easiest way was to make a miniscule wavy bend on the shutter blades, so the friction of the shutter sandwich is just enough to resist the gravitational pull on the blades.
After some trial and error on the test-rig I finally ended up with a friction brake that didn't hinder shutter movement even at the low-energy 2.5V 60mA pulses, yet prevented the blades from changing their angle on their own. As luck should have it, it's a clear night tonight. And not a single shutter failure, yet.
Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-64384485275019741332013-09-20T23:44:00.001+03:002013-09-25T23:50:54.221+03:00Shutter repairs<div style="background-color: rgba(255,255,255,0.5); float: right; margin: 10px; width: 280px;">
<a href="http://www.flickr.com/photos/mickut/9842405043/" title="photo sharing"><img alt="" src="http://farm6.staticflickr.com/5332/9842405043_20b09f8f98_m.jpg" style="border: solid 2px #000000; margin: 10px;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;"><a href="http://www.flickr.com/photos/mickut/9842405043/">Testing a shutter</a><br />The full-sized image has lots of annotations for you to check out.<br /><a href="http://www.flickr.com/photos/mickut/"></a></span></div>
The shutter on my SXVR-H18 CCD-camera broke after three years of use, so I e-mailed the manufacturer to order one or two shutter modules as spare parts. Unfortunately they didn't have any in stock, but a day or two later I received an email saying I've been sent a box with a few old shutter modules in an unknown condition. That box arrived today in a thoroughly crushed shape, containing five nearly intact shutter modules in plenty of bubblewrap. They were apparently from various stages of manufacturing as they were all fairly different. The structure was the same in all (obviously, as they are for the same camera) but the electronics (current limiters and a parallel caps), shutter blades and mechanism substrates were all different among the modules. This was going to be fun.<br />
<br />
I made a small 2-pin test-harness for the motor power connector to check the electro-mechanics, quickly tested all modules and none worked properly (could be from the rough handling of the package). So I disassembled all the shutters and sorted the parts based on condition. After the sorting thru the pieces I came out with three busted motors
(two are needed per shutter), three pairs of warped, uncoated shutter
blades and three working shutter.I had enough one the good parts pile to build at least one, most likely three, possibly even four working shutters modules. I decided to build three as making the fourth would require a bit more tools than I had taken out for the job.<br />
<br />
The test-rig for the assembled shutter-modules was rather simple and I didn't even take a picture of it.
Just a wide rubber band (visible in above image, too) to keep the
shutter from over-extending and the same 2 pin connector for power from the bench
supply as for motor tests. Tapping the pin-header on the shutter opens or closes the blades
depending on polarity, and the motion stops against the rubber band.<br />
<br />
The image is from testing one of the refurbished shutter modules on the camera (I should probably cut a smaller bit of antistatic mat for the computer desk as well to be on the safe side). Although all three were just fine with my test-rig, at first only one of those worked on the camera it self. Once I re-measured a rough estimate on the actual camera shutter signal, I lowered my test-rig voltage to 2.5V and limited the current to 60mA. With these I was able to repeat the performance on camera, and an hour or two later I finally had three fully functional shutter modules.<br />
<br />
Out of curiosity I check the failed motors in more detail. The motors are small, 6mm diameter DC-motors with an equally tiny planetary gearbox. A shutter blade is press-fitted on the output shaft. Two of the broken motors were burnt or stuck and didn't turn at all, and the motor from my camera had it's planetary gearbox shred to powder, but the motor itself works just fine. I guess the cold winter nights can have an effect on polymers and they simply can't take the stress at low temperatures (below -30°C on clear winter nights).<br />
<br />
In theory I should be able to rebuild one more shutter when the current installed one fails, and if these last at least a season each I should be OK till a proper replacement for the KAF-8300 sensor arrives. My requirements for a replacement are quite simple: no mechanical shutter, same diagonal or more, roughly the same pixel size. And a backlit sensor with better QE, especially on Ha-band, would be nice.<br />
<br />
Now all that's left to do is to get a small bottle of argon, go to a clean place, recall how to completely clean a CCD-sensor, re-dry the humidity eaters and reassemble the camera in an argon-bath, so I don't have to worry about sublimated ice on the sensor surface.Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-80681331746838669012013-09-08T22:35:00.002+03:002013-09-08T23:22:24.410+03:00I never bin my color channels more than luminanceAnd here's why: When you're working on an LRGB image set, many frequently stack the images channel by channel, and then combine the RGB to chrominance and L to luminance. In doing so, you're throwing away good luminance data.<br />
<br />
With most of the LRGB filter sets the Red, Green and Blue filters cover combined nearly the exact bandwidth of the Luminance filter. So exposing the same duration at same binning on all filters means I can sum each RGB sequence to an additional L frame, and I've "wasted" only two frames' worth of exposure time from luminance data. If I shot the RGB with a higher binning and different exposure, all that time would be wasted from luminance and my color channels would be crappier due to worse spatial resolution.<br />
<br />
Binning your color channels is beneficial only when you have really dark skies and the sky noise doesn't drown out the read-noise with any sensible exposure durations. If your luminance exposures are easily longer than sky limited color channels at 1x1 binning, you are wasting time and resolution by binning the colors. There's no need to expose at the shortest possible sky-limited times, it should be considered the minimum exposure time, and the maximum exposure time is set by saturation of your target on sensor.<br />
<br />
As a case study, below are two full-resolution crops of the same spot in <a href="http://www.flickr.com/photos/mickut/9703615596/lightbox/" rel="nofollow">my M31 mosaic </a>showing the difference. The mosaic is a 2 by 2 panels, each panel is made from 10 minute exposures, 6 for L and 5 for RGB each.<br />
<br />
<div style="margin: 10px;">
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgFilTyh0Uyyu2uo16kVC3mDO1hG6QPs0Kxi1lcei6ocnJJjBbOdBYvbg7xKRRMGTmXqFVRNE3O2P4ooAEA0vJVAc52lTz1lCJZ13Z003FgZj8HTm4UK6BwY0bkYVwcHd2lH8jvmpdEOOQ/s1600/stacked-L.jpg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgFilTyh0Uyyu2uo16kVC3mDO1hG6QPs0Kxi1lcei6ocnJJjBbOdBYvbg7xKRRMGTmXqFVRNE3O2P4ooAEA0vJVAc52lTz1lCJZ13Z003FgZj8HTm4UK6BwY0bkYVwcHd2lH8jvmpdEOOQ/s1600/stacked-L.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Stack of six 10 minute luminance frames</td></tr>
</tbody></table>
</div>
<div style="margin: 10px;">
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0__mDvWNiR-gMA6KrArr7kkGOXXV9LmVEntnGQZAKUZ8bKA7vSoWxtjVtMK7uH0q5pSzV0sBeb4I5GFSJiBWwVlgl1ZK7QgiaMMsB1VrrVgRkrHFEkzxPf_8G_ilR7KUAPM56iu7Hq50/s1600/stacked-LRGB.jpg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0__mDvWNiR-gMA6KrArr7kkGOXXV9LmVEntnGQZAKUZ8bKA7vSoWxtjVtMK7uH0q5pSzV0sBeb4I5GFSJiBWwVlgl1ZK7QgiaMMsB1VrrVgRkrHFEkzxPf_8G_ilR7KUAPM56iu7Hq50/s1600/stacked-LRGB.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Stack of same 6 luminance frames and 5RGB-sums.</td></tr>
</tbody></table>
</div>
As you can see, the stack of only L frames is a fair bit noisier, and it has a faint
satelite streak going thru as there wasn't enough data to weed out all
traces of it.<br />
<br />
For the lower image, each RGB-set was summed as a synthetic luminance frame, and these 11 luminance frames were stacked for the final image. Some care must be take of course, don't normalize your RGB frames when calibrating, that could throw you data a bit off.<br />
<br />
Some image processing (like PixInsight) allow you to weight the combination based on noise modelling. This does seem to return a decent approximate of a sum, if you have normalized the color frames during calibration.<br />
<br />
<br />Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-74390166622901265922013-04-22T00:56:00.001+03:002013-04-22T01:03:17.525+03:00Season Finale
The end of another astrophotography season has come and passed. I managed to shoot two more targets on the last night of astronomical darkness of the 2012-2013 imaging
season. The moon-lit astronomical darkness lasted for a whopping 14
minutes, the next few dark minutes are due in late August. The moon was at 70% full, but as most of the snow had melted the sky bacground brightness was pretty OK, it stayed level for about an hour on both side of proper midnight.<br />
<br />
<br />
<br />
<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a href="http://www.flickr.com/photos/mickut/8668709267/" title="photo sharing"><img alt="" src="http://farm9.staticflickr.com/8392/8668709267_88617bedb4_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;"><a href="http://www.flickr.com/photos/mickut/8668709267/">Season Finale</a><br />Originally uploaded by <a href="http://www.flickr.com/photos/mickut/">Mickut</a></span></div>
The comet C/2011 L4 PANSTARRS has moved way up north. It was roughly half way up between Shedir and Caph (the two "right-most" stars in Cassiopeia's W-shape)<i>.</i><br />
<br />
Due to it's northern position and the poor visibility north, I was able to image this only for half an hour in the waxing twilight before the comet was obscured by trees. With an hour or two more I might have been able to get a bit better stars on the background as the comet would have moved further during the stack.<br />
<br />
LRGB 9x 1 minute per channel, double stacked (comet + stars).<br />
<br />
<br />
<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a href="http://www.flickr.com/photos/mickut/8668928237/" title="photo sharing"><img alt="" src="http://farm9.staticflickr.com/8121/8668928237_d4d22907bc_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;"><a href="http://www.flickr.com/photos/mickut/8668928237/">Messier 13</a><br />Originally uploaded by <a href="http://www.flickr.com/photos/mickut/">Mickut</a></span></div>
The very last deep sky image on the 2012-2013 astrophotography season was the Messie 13, a large globular cluster in Hercules. The image is stacked from six 5 minute exposures with LRGB filters. This does kill a bit of the interesting bits in the center, but brings out a lot of background galaxies.Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-26910737805688609762013-03-17T22:37:00.001+02:002013-03-17T22:37:18.156+02:00Bode's nebula and friends<div style="float: right; margin-left: 10px; margin-bottom: 10px;"><a href="http://www.flickr.com/photos/mickut/8565394017/" title="photo sharing"><img src="http://farm9.staticflickr.com/8390/8565394017_c611cec39e_m.jpg" alt="" style="border: solid 2px #000000;" /></a><br /><span style="font-size: 0.9em; margin-top: 0px;"><a href="http://www.flickr.com/photos/mickut/8565394017/">Bode's nebula and friends</a><br />Originally uploaded by <a href="http://www.flickr.com/photos/mickut/">Mickut</a></span></div>A rare streak of several clear nights in a row just after new moon gave me an opportunity to expose fairly deep in all channels. I have in total almost 40 hours of exposures for this target with Luminance, Red, Green, Blue, SII, Ha and OIII filters, so future renditions with different combinations are possible in the future.<br /><br /><i>Via Flickr:</i><br />The Bode's nebula (Messier 81, which is actually a grand spiral galaxy), the Cigar galaxy (Messier 82) and NGC 3077 in a family portrait. Seen around the galaxies, but much closer, is faint dusty wisps from our galaxy the Milky Way, in the form of Integrated Flux Nebula illuminated by all the Milky Way's stars.<br /><br />This image is an enhanced color image, combining "traditional" LRGB data augmented with narrowband Ha, SII and OIII emission bands. I wanted to keep the colors quite natural, so as the narrowband emissions not to overpower the scene.<br /><br />Per channel exposures:<br />L: 39x10min<br />R: 33x10min<br />G: 32x10min<br />B: 32x10min<br />Ha: 15x30min<br />SII: 8x30min<br />OIII: 7x30min<br /><br />Total integration time 37 hours 40 minutes<br clear="all" />Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-41344923565447329652012-12-05T21:02:00.000+02:002012-12-05T21:39:53.254+02:00Tähtikuvankäsittelyn perusteita, pinoaminenModerniin harrastajatähtikuvaukseen liittyy väistämättömänä osana monia keskustelupalstoja, joilla kysytään usein neuvoa muilta harrastajilta. Innokkaita, kokeneita auttajia foorumeilta löytyy usein, valitettavasti joukko harhaluuloja on päässyt pesiytymään perimätiedoksi asti. Yritän tämän talven aikana kirjoittaa kustakin isommasta osa-alueesta oman pienen pätkelmän, joista ensimmäisenä on vuorossa tähtikuvien käsittely.<br />
<br />
Tähtikuvaukseen liittyy selviä eri vaiheita itse kohteen kuvaamisen ja "perinteisen" kuvankäsittelyn lisäksi: valinta, kalibrointi, rekisteröinti ja pinoaminen. Niihin kaikkiin kuuluu pieni määrä "pakollista" matematiikkaa, jonka perusteiden ymmärtämiseen on hyvä käyttää hetki aikaa. Oma lähtökohtani kuvankäsittelylle on yksinkertaisuus ja toistettavuus, jolloin voin jatkaa kutakin kohdetta useiden öiden valotuksilla.<br />
<br />
<h3>
Valinta</h3>
<br />
Aina ei kannata ottaa aivan kaikki kuvia käsittelyyn, vaan poistaa listasta kriteerit täyttämättömiä valotuksia. Kuvien valinnassa voi käyttää yksinkertaista luokittelua tähtien tarkkuuden mukaan: tilastollisilla menetelmillä suurempia kuvamääriä pinottaessa lopullinen tarkkuus on likipitäen lähdekuvien tarkkuuden mediaani. Eli kun järjestät kuvat niiden keskimääräisen FHWM-arvon mukaan, voit suoraan valita kaksi kertaa niin monta kuvaa kuin se, jonka FWHM on lähinnä haluttua kuvanlaatua. Yksittäiset epätarkat ruudut eivät siis pilaa koko settiä, jos käytettävissä on kymmenkunta hyvää valotusta.<br />
<br />
Käytännön esimerkkinä parin kuvasarjan FWHM-lukuja:<br />
<br />
<table>
<tbody>
<tr>
<td><b>SarjaA</b></td><td>2.1</td><td>2.2</td><td>2.2</td><td>2.3</td><td>2.3</td><td>2.3</td><td>2.6</td><td>2.8</td><td>3.4</td><td>4.7</td>
</tr>
<tr>
<td><b>SarjaB</b></td><td>1.8</td><td>1.9</td><td>2.1</td><td>2.2</td><td>2.4</td><td>2.4</td><td>2.4</td><td>2.5</td><td>2.5</td><td>2.5</td>
</tr>
</tbody></table>
<br />
Näistä SarjaA tuottaisi todennäköisesti tarkemman lopputuloksen kuin SarjaB, vaikka nuo kaksi epätarkinta kuvaa jätetäänkin pinottaviksi, eikä pinon tarkkuus paranisi vaikka ne jätettäisiin pois.<br />
<br />
<h3>
Kalibrointi </h3>
<br />
Koska kohteet ovat yleensä hyvin himmeitä ja kuvausolosuhteet vaihtelevat pitkin yötä kuun ja muiden asioiden vaikutuksesta, on raakakuvat yleensä ensin kalibroitava. Kalibroinnilla pyritään poistamaan laitteiston aiheuttamat epäkohdat kuvamateriaalista ja siihen käytetään kolmea erilaista "kuvatyyppiä": bias-, flat- ja darkruudut.<br />
<br />
Biasruudut ovat lyhyimpiä mahdollisia valotuksia, joita käytetyllä kameralla saa otettua. Näillä valotuksilla voidaan poistaa kuvista (niin raakakuvat, kuin muut kalibrointikuvat) kameran bias-taso, sekä lukuelektroniikan aiheuttamat vakioituvat kuviot, kuten viivat ja gradientit. Vastoin usein kirjoitteua olettamaa lukukohinaa ei voi poistaa, sitä voi vain lisätä. Tämän vuoksi biasruutuja on hyvä ottaa useita, jotta todellisen lukukohinan vaikutus saadaan minimoitua. Biasruudut pinotaan yleensä suoraan mediaanina, joskin muitakin tapoja on ja erilaisilla mallinusmenetelmillä saadaan varsinaisen lukukohinan osuus poistettua lähes kokonaan. Kameran lämpötilalla ei yleensä ole merkitystä, järjestelmäkameralla kannattaa käyttää samaa ISO-arvoa kuin jolla kuvaa. Biasruuduista pinotaan niinsanottu master-bias, jota käytetään kalibroinnissa yksittäisten biasruutujen sijaan. Täten biasruutuja kannattaa kuvata kerralla riittävästi, vähintään kymmeniä, etteivät ne osaltaan lisää kohinaa lopulliseen kuvaan. Biasruutuja ei tarvitse uusia jokaisen kuvauskerran välillä, kerran pari vuodessa riittää, eikä alkuperäisiä yksittäisiä biasruutuja ole tarve säilyttää.<br />
<br />
Flatruudut ovat yksi tärkeimmistä kalibrointiruututyypeistä, sillä niillä pyritään poistamaan kuvauslaitteiston aiheuttamia ongelmia, kuten vinjetointi ja pölypallerot. Flatruudut otetaan muun kuvauksen yhteydessä, ennen tai jälkeen varsinaisen kuvaamisen, ja kohteena käytetään mitä tahansa tasaisesti valaistua kohdetta. Yleisimmät ratkaisut ovat tasaisesti valaistu T-paita, EL-kalvo ja ilta-/aamuhämärän taivas sopivasta kohtaa. Flatruutuja tulee ottaa jokaisella suotimella erikseen, ja aina
ennenkuin kääntää kameraa johonkin toiseen asentoon tarkentimessa. Flatruudut eivät ole käyttökelpoisia semmoisenaan, vaan niistä täytyy ensin vähentää bias ja pinota master-flatruuduksi. Riittävä määrä on noin 20-30 per suodatin ja niiden kirkkauden tulisi pysyä kameran lineaarisella alueella ja ruudun keskiarvon tulisi olla hieman alle puolet kennon maksimikirkkaudesta. <br />
<br />
Darkruudut ovat kalibrointiruuduista se ainoa valinnainen. Monilla nykyisillä DSLR-kameroilla tapahtuu monenlaista jälkiprosessointia myös RAW-kuville, ja useiden jäähdytettyjen CCD-kameroiden pimeävirrat ovat niin vähäisiä, ettei darkruuduille ole usein tarvetta. Darkruuduilla pyritään poistamaan kalibroitavista kuvista kennon pimeävirtaa sekä kuumia pikseleitä, ne otetaan samassa kuvauslämpötilassa kamera tulpattuna ja ovat valotusajaltaan samanmittaisia varsinaisten valotusten kanssa. Darkruutujen ottaminen on täten hidasta, ja niitäkin tarvitaan useita (kymmeniä) kohinan lisääntymisen minimoinniksi. Darkruudut pitää myös kalibroida biasruuduilla ennen käyttöä.<br />
<br />
Neljäntenä, nykyään lähes kokonaan unohdettuna on flatruutujen darkruudut, teoriassa nekin pitäisi ottaa ja vähentää flatruudusta (bias-kalibroituina toki), mutta nykyisillä kameroilla parin sekunnin valotukset eivät merkittävästi eroa biasruuduista.<br />
<br />
Pimeäsignaali vähennetään kuvasta ennen flat-korjausta, muutoin myös pimeäsignaalin aiheuttamat virheet muuttuvat. Normalisoitu flatruutu tarkoittaa kuvan kunkin pikselin arvon jakamista flatruudun kaikkien pikseleiden keskiarvolla. Tällöin pölypallojen kohdalla olevat keskiarvoa tummemmat pikselit saavat arvon hieman alle 1 ja kuvan yleensä kirkkaampi keskialue saa arvokseen hieman yli 1. Jakamalla valotus tällä normalisoidulla flatruudulla kirkastaa pölypallojen kohtia ja tummentaa kirkkaita kuvakentän alueita.<br />
Itse kalibrointi onkin varsin helppo esittää matematiikan avulla:<br />
<blockquote class="tr_bq">
Kalibroitu = ((Valotus-Bias) - (Dark-Bias))/normalisoitu(Flat-Bias [- (FlatDark - Bias)]) </blockquote>
Oikein tehdyn kalibroinnin jälkeen alkuperäisiä kuvia ei teoriassa tarvita, kunhan käytetyt kalibrointi-masterit ovat tallessa (ja tiedetään millä yhdistelmällä kuvat on käsitelty).<br />
<br />
<h3>
Rekisteröinti</h3>
<br />
Kun kuvat on saatu kalibroitua, on edessä prosessin toinen vaihe. Tässä vaiheessa valitaan yleensä yksi viitekuva, jonka mukaan kaikki muut kuvat asetellaan. Rekisteröintiin on monia tapoja, yleisin on käyttää vähintään kahden tähden avulla tehtävää uudelleenasemointia, jolloin kuvakentän todennäköinen pieni kiertyminen saadaan kumottua. Mosaiikkikuvaamiseen liittyy omat niksinsä, niistä kirjoitan myöhemmin erikseen.<br />
<br />
Rekisteröinti kannattaa suorittaa kaikille kuville saman viitekuvan perusteella, tällöin eri suotimien läpi kuvatut kanavat osuvat automaattisesti kohdakkain. Rekisteröinnissä kutakin kuvaa siirretään, kierretään ja skaalataan siten, että sen tähtikenttä täsmää mahdollisimman tarkasti valittuun viiteruutuun. Näitä rekisteröityjä ruutuja käytetään seuraavissa vaiheissa, mutta käsittelyn jälkeen niitä ei tarvitse varsinaisesti säilyttää, jos on merkinnyt viiteruudun talteen.<br />
<br />
<h3>
Pinoaminen</h3>
<br />
Viimeinen varsinaista kuvankäsittelyä edeltävä vaihe on ruutujen pinoaminen. Kalibroidut, rekisteröidyt kuvat pinotaan per kanava omaksi lopulliseksi ruudukseen. Käytettävissä olevien valotusten määrä vaikuttaa pinoamisessa käyttökelpoisimpaan tapaan. Hyvin pienillä määrillä vaihtoehtoja on noin kaksi: summa ja keskiarvo. Isommalla määrällä valotuksia voidaan käyttää tilastollisia menetelmiä, joiden avulla päästään eroon satelliittien ja kosmisten säteiden aiheuttamista häiriöistä.<br />
Tilastollisille menetelmille yhteistä on se, että kalibroidut kuvat pitää normalisoida vielä keskenään ennen varsinaista pinoamista. Vaikka pinoamisohjelmat suorittavatkin tämän toiminnan puolestasi, mutta sitä ei kannata silti unohtaa lukiessa erilaisia tulkintoja tilastollisten pinoamismenetelmien toiminnasta. Joillain pinoamisohjelmilla tähän keskinäiseen normalisointiin voi valita käytettävän menetelmän, toisilla taas ei. Syy normalisointiin löytyy kohteen ja kaukoputken välistä, samankin illan aikana otetuissa kuvissa taivaan kirkkaus voi vaihdella kohteen lipuessa valosaasteisesta horisontista kohti tummaa taivaanlakea.<br />
<br />
Pinoamistapojen toimintaa voi tarkastella helposti rekisteröidyn kuvapinon yksittäisen pikselipaikan suhteen. Oletetaan, että kuvan keskellä on kiintoisaa kohdetta ja kunkin kanavan osalta kyseiselle pikselille tulee vaikkapa seuraavanlaiset arvot:<br />
<table>
<tbody>
<tr><td><b>R</b></td><td>101</td><td>105</td><td>100</td><td>103</td><td>105</td><td>109</td><td>140</td><td>97</td><td>110</td><td>102</td></tr>
<tr><td><b>G</b></td><td>92</td><td>91</td><td>92</td><td>93</td><td>97</td><td>99</td><td>91</td><td>80</td><td>87</td><td>92</td></tr>
<tr><td><b>B</b></td><td>100</td><td>103</td><td>101</td><td>95</td><td>247</td><td>110</td><td>104</td><td>102</td><td>105</td><td>103</td></tr>
</tbody></table>
<br />
Keskiarvona saadaan (R=108, G=91, B=117), jossa kirkkaan "satelliitin" aiheuttama viiru on selvästi nähtävillä B-kanavan keskiarvossa. Tilastollisilla menetelmillä näistä poikkeusarvoista voidaan päästä eroon, ja tunnetuin tapa on käyttää "sigma-clip" -menetelmää. jokaiselle kohdalle lasketaan kunkin pikselin tilastolliset ominaisluvut mediaan ja keskihajonta, jota merkitään kreikkalaisella aakkosella sigma. Näiden laskemiseen minkäänlaisella tarkkuudella vaatii riittävän määrän osavalotuksia, pitäisin miniminä viittä valotusta.<br />
<br />
Kunkin kanavan mediaanit ovat (R=105, G=92, B=103) ja keskihajonnat (R=11.3, G=4.9, B=43.5).<br />
Mediaania voi käyttää sellaisenaan esimerkiksi bias- ja darkruutujen pinoamisessa. Sigma-clip menetelmässä hylätään yli tietyn etäisyyden päässä olevan arvot ja etäisyys ilmoitetaan keskihajonnan kertoimena: yksi sigma keskiarvosta kumpaankin suuntaan kattaa 68,26% arvoista ja kaksi sigmaa kattaa 95,44%.<br />
<br />
Poistamalla jokaisesta kanavasta yli yhden sigman päässä olevat arvot (R=9, G=7 ja B=9 arvoa), voimme laskea uudet Sigma-clip -keskiarvot: (R=104.7, G=91.1, B=102.6) ja aluksi sinertävältä vaikuttava pikseli muuttuikin punertavaksi. Puolen sigman rajauksella punaisesta kanavasta hylätään jo 4 arvoa ja keskiarvoksi tulee 107, vihreällä kanavalla 92 ja sinisellä 103:<br />
<table><tbody>
<tr><td><b>R</b></td><td><strike>101</strike></td><td>105</td><td><strike>100</strike></td><td>103</td><td>105</td><td>109</td><td><strike>140</strike></td><td>97</td><td>110</td><td>102</td></tr>
<tr><td><b>G</b></td><td>92</td><td>91</td><td>92</td><td>93</td><td><strike>97</strike></td><td><strike>99</strike></td><td>91</td><td><strike>80</strike></td><td><strike>87</strike></td><td>92</td></tr>
<tr><td><b>B</b></td><td>100</td><td>103</td><td>101</td><td><strike>95</strike></td><td><strike>247</strike></td><td>110</td><td>104</td><td>102</td><td>105</td><td>103</td></tr>
</tbody></table>
<br />
Monissa ohjelmissa voi määritellä eri sigma-kertoimet keskiarvon ylä- ja alapuolelle, mutta vaikutus on vastaava.<br />
<br />
Kanavia ei kannata sekoittaa pinoamisvaiheessa, varsinkaan tilastollisilla menetelmillä pinottaessa. Varsinkin kapeakaistakohteissa kanavien väliset erot voivat olla todella jyrkkiä (esimerkiksi harsosumu), joten katsotaanpa miten 10 pikseliä leveälle yksiriviselle kuvalle käy, kun kohteessa on vain "yksivärisiä" kirkastumia. Tässä rivin kunkin kanavan arvot:<br />
<br />
<table><tbody>
<tr><td><b>R</b></td><td>101</td><td>224</td><td>342</td><td>221</td><td>102</td><td>100</td><td>101</td><td>102</td><td>101</td><td>102</td></tr>
<tr><td><b>G</b></td><td>103</td><td>101</td><td>102</td><td>100</td><td>102</td><td>101</td><td>102</td><td>101</td><td>103</td><td>101</td></tr>
<tr><td><b>B</b></td><td>102</td><td>100</td><td>103</td><td>101</td><td>101</td><td>102</td><td>223</td><td>401</td><td>301</td><td>102</td></tr>
<tr><td><b>K-a</b></td><td>102</td><td>141</td><td>182</td><td>140</td><td>102</td><td>101</td><td>142</td><td>201</td><td>168</td><td>102</td></tr>
<tr><td><b>S-clip</b></td><td>102</td><td>100</td><td>102</td><td>100</td><td>102</td><td>101</td><td>101</td><td>101</td><td>102</td><td>102</td></tr>
</tbody></table>
<br />
Sininen ja punainen kirkastuma katosivat Sigma-clip pinosta, eikä tätä oikein voisi käyttää luminanssina tulevalle kuvalle (siitä miksi kannattaa tehdä erillinen L-kuva jos on kuvannut vain RGB-kanavia, lisää seuraavassa postauksessa).<br />
<br />
Pinoamisen jälkeen jäljellä on enää yksi kuva kustakin kuvatusta kanavasta ja niiden yhdistäminen kuuluukin jo kuvankäsittelyn alueelle ja ansaitsee oman kirjoituksensa.Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-26856080713556987142012-10-27T15:55:00.001+03:002012-10-27T17:08:01.708+03:00IC5068 H alpha<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a href="http://www.flickr.com/photos/mickut/8127471993/" title="photo sharing"><img alt="" src="http://farm9.staticflickr.com/8183/8127471993_4d87385e68_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;"><a href="http://www.flickr.com/photos/mickut/8127471993/">IC5068 H alpha</a><br />Originally uploaded by <a href="http://www.flickr.com/photos/mickut/">Mickut</a></span></div>
The weather hasn't really played along with astrophotography as a hobby. It rained almost non-stop for almost two months and the nearly rainless days and nights were completely overcast. The clouds thinned out enough to shoot thru for a hour or so, even then it was a 3/8 cloudy sky.<br />
I wasn't certain what I'll get for this target, the chart showed emission and dark nebulae as targets, so I decided to take a look. It's a bit larger than my FOV, so framing was a compromise to get the interesting filaments in view. Does it look like a bat to you too?<br />
<br />
<br />
<i>Via Flickr:</i><br />
The IC 5068 sits below the North-America and Pelican nebulae, it's a fairly large emission target with many dark dust filaments (AFAIK) about half way between the nebula and us.<br />
Narrowband H-alpha, 3x 20min exposures.Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-86295554953716310862012-08-26T17:25:00.001+03:002012-08-26T17:28:07.852+03:00Obscured by clouds<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a href="http://www.flickr.com/photos/mickut/7863834210/" title="photo sharing"><img alt="" src="http://farm9.staticflickr.com/8297/7863834210_56e45cfd13_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;"><a href="http://www.flickr.com/photos/mickut/7863834210/">Obscured by clouds</a><br />Originally uploaded by <a href="http://www.flickr.com/photos/mickut/">Mickut</a></span></div>
The astronomical darkness has finally arrived. At the start of the new season I decided to try my luck with a small mosaic project of the North-America and Pelican nebulae as the objects are fairly bright and the darkness lasts only a short moment for now.<br />
Last night was the first clear night with astronomical darkness lasting a bit under three hours. In four months the astronomical darkness should last for almost 12 hours, a significant difference there.<br />
<br />
<i>Via Flickr:</i><br />
The famous North-America and Pelican nebulae are part of the same vast emission cloud, but the dark dusty clouds between us and the glowing gas shape the view to the familiar shapes.<br />
LRGB 2x2 frame mosaic, 3x5min per channel and panel. Original frame at 100dpi would yield a nice 150x110 centimeter poster, but more light is needed for better SNR and color gradient corrections.Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-21524962591227180532012-08-07T13:18:00.001+03:002012-08-07T13:18:10.583+03:00Fitting the gear<div style="float: right; margin-left: 10px; margin-bottom: 10px;"><a href="http://www.flickr.com/photos/mickut/7713110870/" title="photo sharing"><img src="http://farm9.staticflickr.com/8427/7713110870_605eb784f5_m.jpg" alt="" style="border: solid 2px #000000;" /></a><br /><span style="font-size: 0.9em; margin-top: 0px;"><a href="http://www.flickr.com/photos/mickut/7713110870/">Fitting the gear</a><br />Originally uploaded by <a href="http://www.flickr.com/photos/mickut/">Mickut</a></span></div>The future skycam and SQM housing for Kirkkonummen Komeetta observatory site is made of a 45deg 110mm sewer junction, end caps and clear acrylic domes. The gear is press-fitted into place with thick, heavy foam rubber.<br clear="all" />Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-46467022732444481422012-08-03T15:50:00.000+03:002012-08-03T15:51:21.576+03:00Greener pasturesThe lush green grass has kept me fairly well off the computer during summer time. Early in the season I had a pro take a look at my swing and assign a training program. The results have been encouraging, gaining a club length in distance and significantly reduced the random hook/slice errors per round. Getting longer shots has cause a bit of trouble estimating the right club choic, and fairly frequently I've found myself in situations I couldn't even comprehend earlier. <br />
<br />
Today was a significant exception to the better play regime. It served as a reminder on how well compared to past games I've played this season and the last. But the culprit was easy to identify. Approaching winter and dark skies have stirred a bit of life at the observatory and I'd spent yesterday doing physical labour with a chisel and wooden mallet in hand. The pounding hand was a bit shaken today, and just getting a natural feeling grip was a challenge let along getting a clean, effortless swing in rhythm. Funny how those little things can affect your game.<br />
<br />
Currently the big question is, do I want to upgrade any part of my astrophoto setup for the coming season? The options are fairly limited with a budget available. I could get hyperstar for my own C8, but that would mean getting a 2" filter set and upgrading the rear cell focusing system to an automated one. That's stretching the budget a "bit" beyond the funds. I could hog most of the imaging time from the club William Optics, it gives a good, flat field with a near perfect angular resolution in the Finnish seeing (about 1.75"/px on my camera). The TS-Quad isn't quite as nice for my camera and it would match a C8+Hyperstar in focal length at 420mm (vs 425mm with Hyperstar). And it's a lot slower at f/6.5 vs f/2.1 for the C8 Hyperstar, a difference of over three stops. Hard decisions, and only three weeks to first moment of astronomical darkness for the next season.Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-55258621402211392672012-03-07T17:41:00.000+02:002012-03-07T18:01:11.708+02:00Experiences from "Kellotapuli"<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh27ljulL4sO-4Pdmxwbt2sV-x2TroRxq6nOrKfP9wcOqGZ7m9ZxmQTWgzM4xTfltw1OQU_Ah9PWAoiD3N3ZIEm1z_hrqNWVE_wn9A79t3HjAxX-bzKSa5VVmSFOxWZQ8dYhhOlPStGSpU/s1600/156.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="218" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh27ljulL4sO-4Pdmxwbt2sV-x2TroRxq6nOrKfP9wcOqGZ7m9ZxmQTWgzM4xTfltw1OQU_Ah9PWAoiD3N3ZIEm1z_hrqNWVE_wn9A79t3HjAxX-bzKSa5VVmSFOxWZQ8dYhhOlPStGSpU/s320/156.jpg" width="320" /></a></div>
Kellotapuli (bell tower, clock tower) is the nickname for my astrophotography gear shelter, given its looks. It's a variation on the rolling roof shelter with minimal footprint (120cm x 65cm base) where the top half rolls off east. This enables using a steep 30/60 degree roof (convenient when living 60deg north) and a wall-sized door. Many claimed the tower would topple seeing it standing at close to 2.5m tall on a hill, but the looks deceive. It may be 65cm wide at base, but in that direction at the 1.2m level there's also the 3.5 meters of track bolted to bedrock at the far end.<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhsK2fMPiXM7zGXzM_If8zyk84PJEQ1h9FTuuv4FX_OlyjNca-rNaHr-_scffBBwNSE-VX8ktjH2tAfl9ZSwc6fYGAZUeAM_7H5RnaUHsU1_mk3yXGtirkPXgBmQDs6K6SeliN0SMdGOUQ/s1600/150.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="179" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhsK2fMPiXM7zGXzM_If8zyk84PJEQ1h9FTuuv4FX_OlyjNca-rNaHr-_scffBBwNSE-VX8ktjH2tAfl9ZSwc6fYGAZUeAM_7H5RnaUHsU1_mk3yXGtirkPXgBmQDs6K6SeliN0SMdGOUQ/s320/150.jpg" width="320" /></a></div>
The main design principle was to avoid shoveling snow at winter and this was achieved handsomely. A bit of shoveling is still needed to access the lower compartments where I store the EL-foil for flat fields, but next summer I'll build some additional removable shelving and other fasteners to keep the need for lower comparment access to a minimum. The rails froze over once, that caused a two minute delay opening the box. A reasonable improvement over the "out-house" shelter which necessated shoveling snow for a good hour or more.<br />
<br />
The design was also based on the assumption that this is for astrophotography only, no creature comforts or visual observation conveniences are necessary. There's a small shelf on the north side for a laptop, power and network outlets on the wall, a small ceramic heater keeping dew out during cloudy nights and that's it. The site has a separate, heated cabin for observers, so a remote desktop connection over LAN works wonders. Almost all aspects have been motorized, polar alignment is a bit of an issue with the Synta mounts in fluctuating temperatures. Although it's mounted on a pier the alignment can be off one half a degree if the temperature changes signficantly. This I guess is mostly due to the very long lower altitude bolt contracting at a different rate than the aluminium mount base. Modding the mount base to allow for a shorter lower altitude bolt should solve this problem. The second option for the current mount is to build a completely new alt-az assembly with linear actuators for an automatic polar alignment.<br />
<br />
Over all I'm ready to declare the Kellotapuli a success. Now I can head over to the observatory with camera and laptop in my backbag and start exposing the skies in less than 10 minutes from arrival. The slowest bit now is starting the laptop, running the imaging SW and reaching initial focus. From then on the automation could take over should I have written more scripts, but that's worth a separate blog post later on.Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-28281647322800252682012-02-02T19:33:00.001+02:002012-03-06T13:27:23.888+02:00Pacman nebula NGC281<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a href="http://www.flickr.com/photos/mickut/6803471327/" title="photo sharing"><img alt="" src="http://farm8.staticflickr.com/7169/6803471327_eb442ce185_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;"><a href="http://www.flickr.com/photos/mickut/6803471327/">Pacman nebula NGC281</a><br />Originally uploaded by <a href="http://www.flickr.com/photos/mickut/">Mickut</a></span></div>
Day 4 in learning to use PixInsight is starting to yield results.<br />
I tested morphological star size reduction, selective de-saturation with a star mask and very moderate luminance and chrominance noise reduction with a lightness mask to smooth out the boosted shadows while leaving the brighter, better SNR nebulous areas and stars intact.Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-83965944996889899152011-12-31T13:21:00.000+02:002011-12-31T17:07:30.524+02:00The year 2011 in a couple of pictures and a few more words<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a caption="<b>Snowy observatory</b> taken 2011-01-08 14:20:59, <a href="http://www.flickr.com/photos/mickut/5336519286/">view details on Flickr</a>" href="http://farm6.staticflickr.com/5007/5336519286_fc3377845a_o.jpg" rel="lightbox[past_shots]" title="Snowy observatory"><img alt="" src="http://farm6.staticflickr.com/5007/5336519286_05685bf2a4_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;">Snowy observatory</span></div>
The year began in snowy, wintery weather in the south. After frequent and plentiful snow-storms it often took over an hour to dig out the observatory deck and roll the outhouse off the scope.
<br />
<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a <a="" 02:33:07,="" 2011-01-26="" a>"="" b>="" caption="<b>" details="" flickr<="" href="http://www.blogger.com/%22http://www.flickr.com/photos/mickut/5388409057/%22%3Eview" light"="" light<="" rel="lightbox[past_shots]" second"="" taken="" title=""><img alt="" src="http://farm6.staticflickr.com/5298/5388409057_a67f0f0d89_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;">"Second" light</span></div>
Despite the snowy conditions and random technical problems, I managed to take a successful exposure of the Rosette nebula.
<br />
<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a caption="<b>The test setup</b> taken 2011-01-09 14:34:16, <a href="http://www.flickr.com/photos/mickut/5339064558/">view details on Flickr</a>" href="http://farm6.staticflickr.com/5286/5339064558_eddd8de106_o.jpg" rel="lightbox[past_shots]" title="The test setup"><img alt="" src="http://farm6.staticflickr.com/5286/5339064558_27455b178b_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;">The test setup</span></div>
The mechanical shutter and difficult dew conditions sparked the idea for building a microcontroller based dew heater and flat-frame illuminator controller box. After a few nights of tweaking I had my first protoboard build up and running, the flat-panel light level was adjustable after all.
<br />
<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a caption="<b>Rosette nebula</b> taken 2011-03-08 13:11:43, <a href="http://www.flickr.com/photos/mickut/5508496587/">view details on Flickr</a>" href="http://farm6.staticflickr.com/5016/5508496587_ff4c6094dc_o.jpg" rel="lightbox[past_shots]" title="Rosette nebula"><img alt="" src="http://farm6.staticflickr.com/5016/5508496587_81c01c6679_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;">Rosette nebula</span></div>
At the end of February my "big" project reached its conclusion and my first reasonably good HST palette image ever taken saw the light of day. Rosette nebula in narrowband false color with total integration time of 21 hours was the new par to exceed in coming weeks and months. The project was shot with 2x2 binning since I couldn't get pin-point round stars across the field for some reason with the astro-club's William Optics FLT-110 and the WO FR/FF-III reducer/flattener.
<br />
<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a caption="<b>Center of the Heart nebula</b> taken 2011-03-08 13:18:38, <a href="http://www.flickr.com/photos/mickut/5508506979/">view details on Flickr</a>" href="http://farm6.staticflickr.com/5018/5508506979_a398f2ca53_o.jpg" rel="lightbox[past_shots]" title="Center of the Heart nebula"><img alt="" src="http://farm6.staticflickr.com/5018/5508506979_e26a602dca_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;">Center of the Heart nebula</span></div>
My balcony observatory provided with great views as well. As Cassiopeia slowly dips north it becomes visible from my balcony and I was able to use my Celeston C8 and Hydrogen alpha narrow bad filter to capture the central emission nebula and the Melotte 15 open cluster there-in.
<br />
<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a caption="<b>Kotkatsaari</b> taken 2011-07-17 19:49:19, <a href="http://www.flickr.com/photos/mickut/5982063211/">view details on Flickr</a>" href="http://farm7.staticflickr.com/6012/5982063211_5b231141f9_o.jpg" rel="lightbox[past_shots]" title="Kotkatsaari"><img alt="" src="http://farm7.staticflickr.com/6012/5982063211_0a6a93a74d_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;">Kotkatsaari</span></div>
And what would a summer be without Wene-WiOL?
<br />
<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a caption="<b>Nukkuva kirkkovene</b> taken 2011-07-17 19:46:57, <a href="http://www.flickr.com/photos/mickut/5982060695/">view details on Flickr</a>" href="http://farm7.staticflickr.com/6022/5982060695_90a1d9a9bb_o.jpg" rel="lightbox[past_shots]" title="Nukkuva kirkkovene"><img alt="" src="http://farm7.staticflickr.com/6022/5982060695_0029e2308f_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;">Nukkuva kirkkovene</span></div>
<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a caption="<b>Kuolimolla</b> taken 2011-07-21 19:00:38, <a href="http://www.flickr.com/photos/mickut/5982652038/">view details on Flickr</a>" href="http://farm7.staticflickr.com/6130/5982652038_a8033dee55_o.jpg" rel="lightbox[past_shots]" title="Kuolimolla"><img alt="" src="http://farm7.staticflickr.com/6130/5982652038_c3d4daacc4_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;">Kuolimolla</span></div>
I had taken the task of captain, charting our rowing route with plenty of options for camping, lunch breaks, swimming breaks and other breaks as well as alternate routes for various wind directions. After crossing to lake Kuolimo we had five huge rowing boats in the water at the same time, a veritable armada with an advanced sonic weapon called "a slightly tipsy mixed choir".
<br />
<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a caption="<b>Reposia Espoossa</b> taken 2011-08-05 21:58:37, <a href="http://www.flickr.com/photos/mickut/6015949940/">view details on Flickr</a>" href="http://farm7.staticflickr.com/6124/6015949940_aeb9c1a10c_o.jpg" rel="lightbox[past_shots]" title="Reposia Espoossa"><img alt="" src="http://farm7.staticflickr.com/6124/6015949940_38e65c2c3e_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;">Reposia Espoossa</span></div>
In the fall the nights grew dark again and the Sun gave a few nice lightshows with northen lights. I was trying to take a nice time-lapse for a star-trail pic, but it was ruined with an exceptionally bright display while I was happily asleep. Later in the fall I happened to wander outside while photographing in order to do some visual observations of Jupiter. The sky look ominously bright and fearful of unexpected cloud-covers I wasn't the least worried about ruined exposures after watching a mesmerizing display of green and red filling the sky beyond zenith. Definitely the best Aurora Borealis in southern Finland within nearly a decade.
<br />
<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a caption="<b>WO odottamassa</b> taken 2011-08-19 18:37:53, <a href="http://www.flickr.com/photos/mickut/6072164703/">view details on Flickr</a>" href="http://farm7.staticflickr.com/6185/6072164703_b46e9bb601_o.jpg" rel="lightbox[past_shots]" title="WO odottamassa"><img alt="" src="http://farm7.staticflickr.com/6185/6072164703_850ace9800_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;">WO odottamassa</span></div>
Being fed-up with all the snow last winter I built a minimalistic rolling-roof observatory box at Komakallio. It's just barely big enough to fit the WO FLT-110 as well as my C8.
<br />
<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a caption="<b>Board with no name?</b> taken 2011-09-17 17:24:06, <a href="http://www.flickr.com/photos/mickut/6155771707/">view details on Flickr</a>" href="http://farm7.staticflickr.com/6162/6155771707_0503a3bda3_o.jpg" rel="lightbox[past_shots]" title="Board with no name?"><img alt="" src="http://farm7.staticflickr.com/6162/6155771707_ca3a3cc950_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;">Board with no name?</span></div>
My project for controlling the dew heater and flat-box took a step forward when my PCBs arrived. "All" I have left now is putting it into a case, write the firmware and PC-end control-SW plus add a few sensors for sky-temp, air-temp, relative humidity and ambient illumination.
<br />
<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a caption="<b>Elephant's trunk</b> taken 2011-09-28 20:39:10, <a href="http://www.flickr.com/photos/mickut/6192768272/">view details on Flickr</a>" href="http://farm7.staticflickr.com/6006/6192768272_d04695134c_o.jpg" rel="lightbox[past_shots]" title="Elephant's trunk"><img alt="" src="http://farm7.staticflickr.com/6006/6192768272_f3eaa3a8f7_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;">Elephant's trunk</span></div>
The annoying star-shapes issue was solved. The WO FR/FF-III reducer/flattener doesn't work correctly with larger sensor sizes on the FLT-110 telescope. I bought myself a WO AFR-4 reducer and now the stars are round within 5% in the corners. The Elephant's Trunk nebula shows beautiful details despite the short total exposure.
<br />
<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a caption="<b>Messier 33 - The Triangulum Galaxy</b> taken 2011-10-26 23:14:48, <a href="http://www.flickr.com/photos/mickut/6284264772/">view details on Flickr</a>" href="http://farm7.staticflickr.com/6036/6284264772_5ce2cc397e_o.jpg" rel="lightbox[past_shots]" title="Messier 33 - The Triangulum Galaxy"><img alt="" src="http://farm7.staticflickr.com/6036/6284264772_061d0427e3_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;">Messier 33 - The Triangulum Galaxy</span></div>
My main project was the Messier 33 Triangulum galaxy. This has the second longest total exposure, 14 hours, of my astrophoto projects. It's an LHaRGB image, where the letters stand for Luminance, Hydrogen alpha, Red, Green, Blue. The Luminance channel adds brightness to the whole image, RGB channels add brightness and color and the Ha channel is used here to accentuate the bright red hydrogen regions. It took several attempts to get the colors right, although I'm not yet completely satisfied with this.
<br />
<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a caption="<b>Pleiades exposed</b> taken 2011-11-27 12:59:07, <a href="http://www.flickr.com/photos/mickut/6410633345/">view details on Flickr</a>" href="http://farm8.staticflickr.com/7154/6410633345_40c330f7b6_o.jpg" rel="lightbox[past_shots]" title="Pleiades exposed"><img alt="" src="http://farm8.staticflickr.com/7154/6410633345_ef18020b65_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;">Pleiades exposed</span></div>
My secondary fall-project was the Pleiades, I took an hour and a half from the morning sky in September and later a bit more light for this slightly off-tinted rendition. A bit more training is needed for color grading the shots.
<br />
The December was effectively lost to clouds, better luck next year.Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-58218270970439598862011-11-27T15:03:00.001+02:002011-12-14T17:25:00.227+02:00Instant gratification<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a href="http://www.flickr.com/photos/mickut/6405255513/" title="photo sharing"><img alt="" src="http://farm8.staticflickr.com/7020/6405255513_d54154d1c7_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;"><a href="http://www.flickr.com/photos/mickut/6405255513/">Messier 35 and NGC 2158</a><br />by <a href="http://www.flickr.com/photos/mickut/">Mickut</a></span></div>
The open and globular cluster are as close to instant gratification as you can get in astrophotography. No finicky wisps of nebuloisty to stretch out from the background noise, just simple stars and lots of them at times. I'm not sure how much more I could get out of this frame even if I increased the exposure ten-fold. Effectively "all" the stars are already there and the SNR is quite good, so there isn't much to gain from spending a month exposing the cluster. Unless there's some faint nebulosity lurking in the darkness...Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-21138235508335478912011-09-26T11:26:00.000+03:002011-09-26T11:26:31.820+03:00Syksy ja sumuiset yötSyksyiset pimeät saapuivat taas, valitettavasti syksyn matalapaineetkin tulivat samalla pilviverhoineen. Afrikan tropiikissa alkunsa saaneiden myrskyjen jäänteet kulkevat pitkän kiertoreitin Karibian kautta päätyäkseen Siperian aroille. Siinä missä isot matalapaineet kulkevat parissa päivässä koko USAn itärannikon korkeuden, kestää niillä yhtä kauan ohittaa kapea Suomi, seuraavan rintaman hönkiessä jo niskaan Atlantilla. Tästä seurauksena Suomessa ei syksyllä ole kovinkaan montaa kirkasta yötä, peräkkäisistä kirkkaista öistä puhumattakaan. Matalapaineet tuovat myös mukanaan runsaasti sadetta ja ne harvat kirkkaat, kuulaat päivät päätyvätkin usein sumuisiin öihin, jolloin kaikki peittyy kasteeseen.<br />
<br />
Tähtikuvauksen kannalta sumu on ilkeää, sillä sen läpi ei näe kovin hyvin. Kasteen kanssa on opittu elämään lämmittämällä kohti taivaita osoittavaa optiikkaa niin, että sen lämpötila pysyy kastepisteen yläpuolella. Ilman lämmitystä kirkaalla säällä optiikan pinta jäähtyy alle ympäröivän ilman lämpötilan säteilyjäähtymisestä johtuen, täten kosteassa ilmassa jäähtyminen jatkuu alle kastepisteen. Pahimmillaan kosteutta voi kertyä niin paljon, että linssi voi peittyä kokonaan veteen. Veden suuresta ominaislämmöstä johtuen kertyneen veden poistaminen vaatii paljon energiaa, mutta jo melko pienellä lämmityksellä voidaan pitää optiikan pinta kastepistelämpötilan yläpuolella. Liian suurta määrää lämpöä puolestaan ei kannata käyttää, koska tällöin optiikan sisäiset lämpötilaerot voivat aiheuttaa kuvanlaatuoa merkittävästi huonontavia konvektiovirtauksia putken sisään tai pahimmillaan jopa linssin ulkopuolisen ilman pyörteilyä.<br />
<br />
Näitä optiikan etuelementtien lämmittimiä kutsutaan huurrepannoiksi, ja markkinoilla on useita erilaisia ja erihintaisia ratkaisuja. Lisäksi liiallisen lämmöntuoton estämiseksi usein käytetään säädettävää ohjainta, jolla vallitsevan ilmankosteuden perusteella säädetään lämmitystehoa juuri ja juuri riittäväksi. Nykyään kaupalliset ratkaisut perustuvat lähes yksinomaan paksukalvovastuksesta, jonka käyttäminen kotikonstein on turhan hankalaa, ja saatavuus pienissä erissä lähes nolla. Tee-itse -henkisille on kuitenkin kaksi muuta toimivaa tekniikkaa, yleisin ratkaisu on juottaa suuri määrä vastuksia rinnan tai sarjaan ja toinen tapa on käyttää vastuslankaa. Sopivan tehontarpeen (ja siten vastuksen) laskemiseen löytyy helppo kaava, <i>P = 0.0606 x D +1.18</i>, jossa D on lämmitettävän elementin halkaisija millimetreinä ja lopputulos on watteja. Tarvittavien vastusten laskemista varten on tehty myös <a href="http://www.iceinspace.com.au/63-292-0-0-1-0.html">kätevä taulukkolaskentapohja</a>. Suomen oloissa kannattaa tehdä hieman ylitehokas lämmitin (kosteimpina kevättalven öinä sulavasta hangesta vapautuva vesihöyry tuottaa helposti kaiken jäähän kuorruttavat olosuhteet), sillä tehoa on helpompi säätää pienemmäksi kuin suuremmaksi.<br />
<br />
Huurrepantojen säätöelektroniikkaa on saatavilla vaihtelevin hinnoin, kalleimpien ollessa useita satoja euroja. Tee-itse ohjaimen saa tehtyä helpoimmillaan muutamalla analogisella komponentilla 555-piiristä PWM-kytkennässä, jolla ohjataan tehotransistoria tai FETtiä, pulssinleveyttä säätämällä voidaan rajoittaa huurrepannan keskimääräistä lämmöntuottoa lähes nollasta täyteen tehoon. PWM-taajuus kannattaa pitää joko hyvin matalana (alle puoli hertsiä) tai kohtuullisen korkeana (muutama kHz), tällöin kuorman kytkennästä aiheutuvat virtapiikit on helpompi suodattaa pois häiritsemästä herkkiä kuvausinstrumentteja. Toinen harrastajan helposti saavutettavissa oleva säätötapa on tuottaa PWM-signaalia mikrokontrollerilla, etuna tällöin on kohtuullisen helppo lisätoimintojen saaminen, esimerkiksi lämpötilan ja ilmankosteuden mukaan automaattisesti säätyvä teho tai tietokoneohjaus USBn kautta. Moderneilla mikrokontrollereilla ulkoisten komponenttien tarve on varsin pieni ja nykyään löytyy myös hyviä TTL-tasoilla ohjattavia FETtejä, jolloin erillistä FET-ohjainpiiriä ei edes välttämättä tarvita.<br />
<br />
Oma automaatioprojektini käyttää USB-ohjattua mikrokontrolleria tuottamaan useita PWM-ohjattuja signaaleja, kaksi on varattu huurrepannoille (toinen kuvausoptiikalle, toinen ohjausoptiikalle), yksi valopaneelille ja kolme on varalla. Lisäksi voin kytkeä mikrokontrolleriin 1-wire -protokollaan käyttäviä antureita mittaamaan kosteutta ja lämpötilaa, sekä erilaisia mekaanisia käyttöliittymäkomponentteja tietokoneettoman käytön säätimiksi. Taloudellisesti mikrokontrolleripohjaiset projektit eivät kannata, jos laskee omalle ajalleen minkäänlaista hintaa, mutta harrastuksena ne tuovat mukavan lisän kuvausöiden kokemukseen.Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-45445866944366315782011-09-21T21:00:00.002+03:002011-09-22T14:47:06.528+03:00William Optics Flattener comparisonI recently acquired the <a href="http://www.williamoptics.com/accessories/flattener4_features.php">William Optics Adjustable Flattener Reducer 4</a> as I wasn't too happy with the image quality I was getting from the local astro-club's William Optics FLT-110 telescope with the <a href="http://www.williamoptics.com/accessories/flattener3_features.php">William Optics Focal Reducer/Field Flattener III</a>. <br />
<br />
<div style="float: right; margin-bottom: 10px; margin-left: 10px;"><a href="http://farm7.static.flickr.com/6076/6121477764_91b53eb03d_o.jpg" rel="lightbox[flattener]" title="WO FR/FF 3 star shapes" caption="Shaped stars with WO FLT-110 and WO FR/FF III (<a href="http://www.flickr.com/photos/mickut/6121477764/">full image on Flickr</a>)"><img alt="" src="http://farm7.static.flickr.com/6076/6121477764_b192afed2f_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;">William Optics FR/FF III</span><br />
<span style="font-size: 0.9em; margin-top: 0px;">50 minutes of Ha in 10min subs</span><br />
<span style="font-size: 0.9em; margin-top: 0px;">Cropped view around target.<br />
</span></div><br />
Although I had used the WO FR/FF III the last season while using the FLT-110, I noticed my star shapes were way off considering how good the scope was supposed to be. I had put the blame on the less than stellar polar alignment of the mount, especially since the mount was secured to the pier and aluminum base plate only by the central bolt. Needless to say, as the temperature during the imaging season fluctuates between +15 C and -35 C, the bolt comes loose due to thermal effects and the mount starts to drift off. During the summer I built a new observatory for a new EQ6 our club had purchased and I made sure the polar alignment won't move. With the mount aligned I discovered that the horrible looking stars were not caused by polar alignment but an optical issue instead. I played around with the flattener to sensor distance and the star images improved a bit, but the stars near border turned from warp effect to cross shapes. Reading thru forums I found out I'm not the only one faced with the same issue on the FLT-110.<br />
<br />
<div style="float: right; margin-bottom: 10px; margin-left: 10px;"><a href="http://farm7.static.flickr.com/6173/6167766162_071ccfda6b_o.jpg" rel="lightbox[flattener]" title="WO AFR-4 star shapes" caption="Relatively sharp stars with WO FLT-110 and WO AFR-4 (<a href="http://farm7.static.flickr.com/6173/6167766162_071ccfda6b_o.jpg/">full image on Flickr</a>)"><img alt="" src="http://farm7.static.flickr.com/6173/6167766162_0eed491d0e_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;">William Optics AFR-4</span><br />
<span style="font-size: 0.9em; margin-top: 0px;">90 minutes of Ha in 10min subs.</span><br />
<span style="font-size: 0.9em; margin-top: 0px;">Nearly full field of stack.<br />
</span></div><br />
After a bit of research I placed an order for the William Optics AFR-4, as it had a reasonably long back focal distance, and more importantly, the flattener lens group location can be moved for 20mm by rotating the lockable adjustment ring. The various posts on forums recommended a distance of 73.5mm for the FLT-110, so I made a rough estimate and started waiting for a break in the clouds. A week later I took another set of frames of the Sh2-101 () so I could make a direct comparison on the images produced by the flatteners using the same equipment. Incidentally the sensor distance was quite good with my first guess and now the sensor tilt is the prominent image quality reducing factor. I was able to reach 1.05px HFR stars at center with the stars in corners were around 1.08 pixels HFR. The image scale is a bit tighter than with FR/FF3, the field of view is 2 arcmin narrower at 97.2 arcmin with the AFR-4 compared to 99.0 arcmin with the best star shapes on FR/FF-III. Of course the field of view with reducers depends on the sensor distance, so the final figure after more adjustments is subject to change.<br />
<br />
So far the only negative aspect has been a bit of flare around brightest star in the field, but it could be partly caused by the humidity, as the air was far from clean on the test night. Hopefully more to follow on the experience with AFR-4 as the imaging season 2011-2012 progresses and I reach a better optical alignment.Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com1tag:blogger.com,1999:blog-7939836829441641427.post-16745241365472157942011-09-17T21:47:00.000+03:002011-09-17T21:50:58.222+03:00But what to call it?<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a href="http://www.flickr.com/photos/mickut/6155771707/" title="photo sharing"><img alt="" src="http://farm7.static.flickr.com/6162/6155771707_ca3a3cc950_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;"><a href="http://www.flickr.com/photos/mickut/6155771707/">Board with no name?</a><br />Originally uploaded by <a href="http://www.flickr.com/photos/mickut/">Mickut</a></span></div>
My automation project for tedious astrophotography tasks reached a new milestone today as I assemebled my new control board for functionality tests. The board has two main duties, one is to control the dew-heater bands and the other, main reason for this, is to control the EL-foil luminosity while taking flat frames. My astro-camera has a mechanical shutter with a limited speed, so the flat frame exposures have to be at least 2.5 seconds to eliminate the shutter movement below a few ADUs. As the LRGB filters pass a lot of light, the light has to be fairly dim to reach such a long exposure with a sensitive camera. Unfortunately, the narrow-band filters are just that: narrow. Using the same low setting on a 7nm SII filter (deep red near infrared) the not-so-warm light of the EL foil is diminished to extinction resulting in almost one minute flat frame exposures. Taking 30-60 exposures at one minute each doesn't sound like something I want to do at 6am, I can now make the light brighter for the narrow band filters keeping the exposure shorter, and brightening the light for wideband filter for extending the exposure.<br />
<br />
<div style="float: right; margin-bottom: 10px; margin-left: 10px;">
<a href="http://www.flickr.com/photos/mickut/6156314032/" title="photo sharing"><img alt="" src="http://farm7.static.flickr.com/6206/6156314032_5320964a15_m.jpg" style="border: solid 2px #000000;" /></a><br />
<span style="font-size: 0.9em; margin-top: 0px;"><a href="http://www.flickr.com/photos/mickut/6156314032/">Board bottom</a><br />Originally uploaded by <a href="http://www.flickr.com/photos/mickut/">Mickut</a></span></div>
I drew the board in KiCad a while ago, and kept upgrading new features, most notably the extra IO-lines were added when I noticed I had an extra ATMega644. A bit of an overlook at the datasheets left me with a grave error in the schema, I had connected the VCCIO pin of the FT232RL to the VUSB instead of VCC network, so I had to cut the trace on the board and jump the SOIC-28 leg to VCC on the ICSP header. Unfortunately I realized this only after my order had already been sent back from iTead Studios, so hacking was necessary.<br />
<br />
This would have been relatively easy, but I had found out that the ATMega644 can run an Arduino compatible bootloader called <a href="http://sanguino.cc/">Sanguino</a> and all I needed was a way to reset the board while programming. I had forgotten the reset switch completely, although one can pull down the reset pin on the ICSP just the same. The Arduino also supports auto-reset over FT232RL by connecting the DTR# -pin to ATMega reset thru a series capacitor (pulsing the reset). Not so fortunately the DTR# -pin is one pin over from the VCCIO and in between there's RST# pin that I don't want to touch at all. Plenty of light, magnification and a narrower soldering tip was used to make the bits of wire go to the right spots without solder bridges.<br />
<br />
The auto-reset isn't fully reliable, I might have used a wrong value cap in the series. The Sanguino bootloader installation made almost miss a heart beat, as it didn't say what it was doing while writing the bootloader. As you can see, my board relias on the internal clock source of the ATMega, and the first thing Arduino IDE does when flashing the bootloader is setting the fuses to use an external clock source. This caused a few minutes of frustration wondering why nothing works, until I realised my ATMega needed a temporary heart transplant. With a 12MHz oscillator I was able to reset the fuses and then it was time to adjust the Sanguino bootloader code and flashing settings to match my setup. Now I'm able to upload Arduino sketches onto my board and they run jst fine, serial data receive excluded (this seems to be a known bug in Sanguino).<br />
<br />
My actual test-code is just basic C-code with avr-libc and avr-gcc. Being able to upload the code thru the Arduino bootloader makes field-upgrades easier, though, since now there's no need to carry the programmer device along. The test-code sets the PWM channels at 50% duty cycle, the fast channels at 4kHz, slow channels at 13Hz and the servo channels at 50Hz with 16bit OCR1 registers for accurate positional control (ICR is set at 19999). The board takes around 10-20mA when operating without load, the possible servos are the only external load on the VCC line keeping the LM7805 from heating up too much. The FETs are N-channel IRF540N, saturating at 4.7 volts, so I can drive them directly with the uC outputs with minimal protective circuitry around the FET. Possible flywheel diodes for inductive loads are omitted, they can be added closer to load if necessary. A bit of probing and coding proved that the circuit works now pretty much as planned, I was able to connect over USB-serial to the uC and change the PWM duty cycle from my computer, and the EL-foil changed its brightness just as expected (non-linearly). For the EL-foil I'm also using a current limiting resistor inline with the load, the 2.2ohm 50W resistor heats up to around 20C above ambient, very close to my estimates on theoretical power dissipation.<br />
<br />
Now it's time to call it a day/night, start thinking about those free IO-lines on the side and plan the firmware and PC-side code a bit further into reality.<br />
<br />
Oh, what to call it? The ability to use the Arduino IDE after all (when the Sanguino UART bugs are fixed) kind of necessitates something Arduinoish and the astrophotography background should somehow be present in the name as well. Thusfar the best name I've been able to come up with is Astruino, and that's what I shall call it from now on.Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-85960977128297709622011-09-07T10:30:00.001+03:002011-09-17T21:51:12.003+03:00Pelican Nebula (IC 5067/5070)<div style="float: right; margin-left: 10px; margin-bottom: 10px;"><a href="http://www.flickr.com/photos/mickut/6120878613/" title="photo sharing"><img src="http://farm7.static.flickr.com/6071/6120878613_07f4f0d9a4_m.jpg" alt="" style="border: solid 2px #000000;" /></a><br /><span style="font-size: 0.9em; margin-top: 0px;"><a href="http://www.flickr.com/photos/mickut/6120878613/">Pelican Nebula (IC 5067/5070)</a><br />Originally uploaded by <a href="http://www.flickr.com/photos/mickut/">Mickut</a></span></div>The Pelican Nebula is located in Cygnus right next to North America Nebula, and it is in fact the same cloud of glowing hydrogen gas. From our point of view the cloud is split in two forming the more photographed N-A nebula and the Pelican nebula by the dark dust between the Earth and the gas cloud.<br /><br />The dark dust has a lot of intricate detail I wanted to bring forward by increasing the local contrast using a contrast mapping algorithm.<br /><br /><i>Via Flickr:</i><br />The Pelican nebula in Hydrogen alpha.<br />Tone-mapped to show the rich low-contrast details, although the "pelicanness" is reduced a bit in the process.<br /><br />Total exposure: 1h30m.<br clear="all" />Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-13614962921228793592011-08-16T22:55:00.003+03:002011-08-16T23:11:49.446+03:00Komakallion KellotapuliHavaintokaudella 2009-2010 havaintoilta Komakalliolla alkoi usein kaivamalla muutama neliömetri satanutta lunta kallioon asti kolmijalkaa varten, ja arvokasta havaintoaikaa kului tähän usein turhankin paljon, varsinkin jäätyneen nuoskalumen kohdalla. Kesän 2010 aikana virisi ajatus tolpan valamisesta lumitöiden vähentämiseksi. Syksyllä 2010 tulikin valettua ison Observatoriokopin luoteisnurkalle tolppa, joka painui kovettuessaan luonnollisesti hieman pohjoisen suuntaan. Tolpan suojaksi löytyi vieläpä sopiva, kookas ja painava suojaputki, jolloin lumitöiden tarve väheni noin puoleen neliömetriin suojaputken päältä. Kaudella 2010-2011 tuli kuitenkin havaittua, että vaikka seurantapään ja kaukoputken tykötarpeineen saa nyt noin vartissa kokoon, kestää napasuuntaus vielä turhauttavan paljon. Varsinkin talvella tuo aika on pois havaintoajasta arkipäivinä, jolloin valoisana aikana ei vielä ehdi paikalle. Kun Komeetta osti EQ6 seurantapään, syntyi tarve tehdä kiinteä säilytyspaikka, jossa aktiivikuvaaja voisi säilyttää lähes valmista, napasuunnattua kuvauskalustoa. Kaudella 2010-2011 Komakalliolla oli usein kolme tai neljä aktiivihavaitsijaa, joten tällaiselle oli selvästikin tilaus.<br />
<br />
Kesällä aktiivikuvaajien keskuudessa pyöriteltiin erilaisia ideoita rullaavista kopeista kääntyviin kattoihin, mutta mikään ideoista ei oikein tuntunut erityisen toimivalta. Pienen mittailun ja mallailun jälkeen oli selvää, että suojakopista on tehtävä pohja-alaltaan pienin mahdollinen, ja se puolestaan rajasi vaihtoehtoja lisää. Rullaava koppi vaatii tasaisen liukualustan ja paljon lumitöitä toimiakseen, liukuva katto taas paljon tilaa tolpan ympärille laitteiston asentamista varten. Taittuvaa kattoakin pohdittiin, mutta ongelmaksi muodostui pelkästään puutavaralle laskettu 25-30kg paino ja hankala saranointi. Heinäkuun alussa keksin ratkaisuksi liukuvakattoisen havaintosuojan ja syrjään rullaavan astrohuussin välimuodon, jossa puolet kopista liukuu syrjään, ongelmana oli vain rullaavan osan suunta. Pohjoiseen ei voinut tehdä kiskoja, koska pääsy "Huussille" eli WilliamOptics -putken suojalle oli tuota kautta. Lännen puolella on parkkitilaa ja kulku työmaakoppiin ja isolle kopille, idässä ja etelässä rajoitteena ison kopin katto ja kiskot. Ison kopin katto ei kuitenkaan rulla aivan kiskojensa päähän ja varmistusmittauksen jälkeen olikin selvää, että kiskot on asennettava noin metrin korkeudelle kohti itää. Tällöin yläosa rullaa ison kopin kiskojen päälle ja ison kopin katto mahtuu yhä aukeamaan kokonaan. Pohjavalu tehtiin heinäkuussa, mittaa pohjalle tuli 120cm etelä-pohjois -suunnassa ja 70cm itä-länsi suunnassa, kiskojen matkustuskorkeudeksi 100cm pohjalaatan yläpinnasta. Näillä mitoilla tarvittava betonin määräkin oli kuljetettavissa henkilöautolla ja valettavissa kahden hengen voimin. Viisi säkkiä, neljä rautaa ja 12 osittain upotettua kierretankoa myöhemmin tolpan ympärillä oli kiiltelevä betonivalu, jonka ulkoreunoja kiersi sojottavat kierretangot rungon pulttausta varten.<br />
<br />
Heinäkuun lopussa sain piirustukset valmiiksi ja tarvelistan laadittua, rakentaminen voi siis alkaa. Kajn kasvihuoneessa työturvallisuudesta tinkimättä sahasimme pohjakerroksen seinävanerit valmiiksi ja kävimme hakemassa muutaman juoksumetrin puuta ja kaksi levyä vaneria. Alin, betonia vasten oleva kerros sahattiin painekyllästetystä 50x100 millisestä puusta, naulattiin kasaan ja kiinnitettiin kierretankoihin. Kopin alempi kotelo sai raamikseen 48mm x 48mm puusta nousut, 50x100 takapalkin ja sivuihin 3.5m pitkät kiskot. Kaikki liitokset rungossa tehtiin talttaamalla loviliitokset ja kiinnittämällä ne liimalla ja ruuvein. Kiskojen peräpäähän pystypuiden pohjaan laitettin pienet, säädettävä tolppakengät, koska kiskojen pään kohdalla kallion kumpuilu ei mahdollistanut tarkkaa mittaan sahaamista, lisäksi näin puu saatiin sopivasti irti kalliosta. Kiskojen päälle löytyi sopivaa 40mm leveää alumiinilattaa, johon porattiin upotetut reiät ruuveille, joskin kiinnitykseen käytettyjen ruuvien kanta erosi hieman upotusten sovitukseen käytetystä ruuvista ja kannat jäivät hieman ylös kaikesta huolimatta. Lattojen alle levitettiin noro polyuretaaniliimaa, ja kiskot ruuvattiin paikoilleen. Kiskojen päälle päätettiin laittaa suuret kuulalaakerit rulliksi, ja yläkopin runkolankkuihin kaivettiin sopivat kolot ja akselireiät. Rakenne on osittain vastaava kuin isossa kopissa, joskin pienempään tilaan mahdutettuna: kuulalaakerit puristetaan holkkien avulla rungon sisään akselireiän kohdalta. Tässä tapauksessa toisella puolella on noin 25 milliä palkin mäntyä ja toisella puolella 15mm vaneri.<br />
<br />
Yläosan rakentaminen puuvalmiiksi sujui myös nopeasti parissa illassa, ainoita hankaluuksia tuotti kattotuolien tarkka mittaaminen, harjakaton kulmat ovat 30 astetta pohjoisella puolella ja 60 astetta eteläisellä puolella. Näillä kattokulmilla saadaan kopin sisätila tehokaasti maksimoitua ja sivupuiden pituudet pidettyä yksinkertaisina sekä seinävanerin kulutus mimimoitua. Avuliaista neuvoista huolimatta ratkaisu löytyi ja rakentaminen eteni päällystämällä kopin seinät vanerilla. Kattomateriaaliksi päätyi paksu kattohuopa, toimistolla sermin toiselta puolelta löytyi ylimääräinen rulla huopaa, jota oli juuri oikea määrä, oikean kokoisina paloina.<br />
<br />
Kattohuovan kiinnityksen ja ovien teon jälkeen oli aika nostaa koko komeus harjakorkeuteensa, hieman reilut kaksi metriä. Torni sai jo runkovaiheessa monia nimiä, kuten kaappikello ja kellotorni, koska itse kopin rakenne on itä-länsi -suuntaan verrattuna hämäävän kapea ja korkea, sillä kiskoja ei juuri mielletä rakenteen kantaviksi osiksi. Korkeus korostuu varsinkin kun tornia katsotaan keskimäärin alarinteestä, parinkin metrin päästä katsoja on lähes metrin tornin kohtaa alempana. Rakenteellisesti torni on tuossa huojalta vaikuttavassa suunnassa hyvin tukeva, tukeutuuhan koko metrin korkuinen alaosa 3.5 metrin matkalle. Yläosaksi jää raskas, 70cm syvä, reilun metrin korkuinen koppero, joka molemmissa ääripäissään pysäköityy ruuvisaranoista tehtyihin kippiestoihin. Sivuttaisliikkeen estämiseksi yläosan molempiin rullapuihin laitettin kaksi sivulaakeria ulkopuolelle ja yksi sisäpuolelle pitämään seinät kiskojen suuntaisina. Näiden kiinnitämisen, lukkosalvan ja ilmastointireikien teon jälkeen koppi olikin valmis maalattavaksi. Komakallion harmaata sävyä en löytänyt mistään järjelliseen hintaan, mutta onneksi funktionaalinen observatorionvalkoinen on maalien perussävystöä. Puunsuoja-aineellista ulkopohjamaalia kului perjantaina kaksi litraa ja lauantai-iltana sen päälle meni kolme litraa öljymaalia. Tätä kirjoittaessa kopista puuttuukin enää sähköpistokkeet, tietoverkkopistoke ja jonkinlainen pieni kosteuden tiivistymisen torjuntaan sopiva lämmityslaite, kuten pienitehoinen hehkulamppu.<br />
<br />
Mitäpä tämän kopin tekemisestä tuli opittua? Ainakin se, ettei suunnitelmiin kannata tehdä muutoksia kesken rakentamisen, vaikka kuinka joku pitää omaa ideaansa parempana. Parissa kohdassa kävi nyt niin, että suunnitelmista poikkeava "helpompi" ratkaisu tuotti useita tunteja enemmän säätötyötä kuin suunnitelman mukaan tehtynä olisi mennyt. Lisäksi rakentamisen loppusuoralla ideanikkarit ajettiin nuotion ääreen paistamaan makkaraa ja kopin läheisyydessä keskityttiin pohdinnan sijaan rakentamiseen piirrustusten mukaan, varsinkin viimeinä isona puutyöiltana, jolloin monia upotuksia ja leikkauksia veistettiin ja jyrsittiin tarkasti mittojen mukaan sivurullille ja ovien heloille. Kaikesta avusta huolimatta valmista tuli, aikaa kului vain yksi viikonloppu ja kahden viikon illat, eli minulta vajaat 40 tuntia ja muilta rakentajilta (keskimäärin eteenpäin auttoivat ainakin Kaj Wikstedt, Lauri Kangas, Panu Lahtinen, Mika Luostarinen ja Samuli Vuorinen) parista tunnista reiluun kymmeneen. Toivottavasti pian sää selkenee, niin pääsen ottamaan kalustosuoja Kellotapulin ensivalot.<br />
<br />
Niin, miksi nimeksi tuli lopulta Kellotapuli? Syyhän on ilmeinen kopin rakenteesta johtuen, eikä pelkästään ulkonäöllisistä syistä: katon eteläpuoli osoittaa lähes suoraan taivaannapaan ja eteläseinä etelään, joten räystääseen kiinnitettävällä katon suuntaisella viisarilla eteläseinään saadaan piirtymään aurinkokello.<br />
<br />
<b>Kuvia</b><br />
Katso <a href="http://www.flickr.com/photos/mickut/sets/72157627342378716/">Kaappikelloprojekti</a>n kuvasarja Flickrissä.<br />
<div style="margin: 0; overflow: hidden; padding: 0; width: 500px;"><br />
<a href="http://www.flickr.com/photos/mickut/6030289230/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Kellotapuli"><img alt="Kellotapuli" src="http://farm7.static.flickr.com/6146/6030289230_5510db5702_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/5086129763/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Tolppaprojektin jalustatesti"><img alt="Tolppaprojektin jalustatesti" src="http://farm5.static.flickr.com/4110/5086129763_7db510e0f6_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/5086128243/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Pilarin liitospinta"><img alt="Pilarin liitospinta" src="http://farm5.static.flickr.com/4144/5086128243_d02cfe62e7_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/5086723048/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Liitoskappaleen kiinnitys"><img alt="Liitoskappaleen kiinnitys" src="http://farm5.static.flickr.com/4087/5086723048_4a1f2977fb_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/5086721966/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Suojaa sateelta"><img alt="Suojaa sateelta" src="http://farm5.static.flickr.com/4088/5086721966_5b344f5843_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/5088732411/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 0 10px 0; width: 75px;" title="Tolppa testikäytössä"><img alt="Tolppa testikäytössä" src="http://farm5.static.flickr.com/4087/5088732411_d23b4a7e15_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><br />
<br />
<a href="http://www.flickr.com/photos/mickut/5990069060/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Improving the pillar"><img alt="Improving the pillar" src="http://farm7.static.flickr.com/6142/5990069060_28632af0dd_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/5990069396/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Casting done"><img alt="Casting done" src="http://farm7.static.flickr.com/6121/5990069396_3849d14c0b_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/5990069744/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Cleaning up"><img alt="Cleaning up" src="http://farm7.static.flickr.com/6134/5990069744_3e776c9598_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/5990070072/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="From above"><img alt="From above" src="http://farm7.static.flickr.com/6146/5990070072_791c48d71f_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/5989509747/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Test fitting the foundation layer"><img alt="Test fitting the foundation layer" src="http://farm7.static.flickr.com/6007/5989509747_8ccef104b1_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/6003244422/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 0 10px 0; width: 75px;" title="Lower frame and rail"><img alt="Lower frame and rail" src="http://farm7.static.flickr.com/6130/6003244422_ab688ab1eb_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><br />
<br />
<a href="http://www.flickr.com/photos/mickut/6002699763/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Frame covered"><img alt="Frame covered" src="http://farm7.static.flickr.com/6122/6002699763_470a1c7204_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/6003247064/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Close-up of the bottom frame"><img alt="Close-up of the bottom frame" src="http://farm7.static.flickr.com/6140/6003247064_e8dc92b6d2_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/6003248356/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Door built and open"><img alt="Door built and open" src="http://farm7.static.flickr.com/6140/6003248356_ea34882ae2_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/6002703377/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Assembled lower box"><img alt="Assembled lower box" src="http://farm7.static.flickr.com/6007/6002703377_85e2d90c48_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/6016007096/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Projekti etenee"><img alt="Projekti etenee" src="http://farm7.static.flickr.com/6021/6016007096_826d9085a7_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/6015455517/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 0 10px 0; width: 75px;" title="Harjan tutkinta"><img alt="Harjan tutkinta" src="http://farm7.static.flickr.com/6008/6015455517_e5a8bdb437_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><br />
<br />
<a href="http://www.flickr.com/photos/mickut/6016009642/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Yläosa puuvalmis"><img alt="Yläosa puuvalmis" src="http://farm7.static.flickr.com/6127/6016009642_543545469e_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/6016004346/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Kiskojärjestelyt"><img alt="Kiskojärjestelyt" src="http://farm7.static.flickr.com/6016/6016004346_8e48b3f23b_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/6015452317/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Testiajossa"><img alt="Testiajossa" src="http://farm7.static.flickr.com/6121/6015452317_cbcc19e163_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/6015453331/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Kellotorni vai kaappikello?"><img alt="Kellotorni vai kaappikello?" src="http://farm7.static.flickr.com/6010/6015453331_863e0a3d1f_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/6029734379/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 10px 10px 0; width: 75px;" title="Takaseinä"><img alt="Takaseinä" src="http://farm7.static.flickr.com/6123/6029734379_c22cce4dc4_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a><a href="http://www.flickr.com/photos/mickut/6030289478/in/set-72157627342378716/" style="display: block; float: left; height: 75px; padding: 0 0 10px 0; width: 75px;" title="Havaintokalusto asennuksessa"><img alt="Havaintokalusto asennuksessa" src="http://farm7.static.flickr.com/6184/6030289478_a68b65ed28_s.jpg" style="border: none; height: 75px; margin: 0; padding: 0; width: 75px;" /></a></div><br />
Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-1426583658763118982011-05-22T19:31:00.001+03:002011-05-22T19:34:52.176+03:00Testing continues<div class="separator" style="text-align: center;"><a href="http://www.flickr.com/photos/mickut/5745664415/" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;" title="22.05.2011 by Mickut, on Flickr"><img alt="22.05.2011" height="240" src="http://farm6.static.flickr.com/5264/5745664415_d914fdcba5_m.jpg" width="320" /></a></div><div class="separator" style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiNdkyHQM4_whwzs1l9dDSuar1MRmdYDNigebod41KYL_9C8HcVZv42rrRle-2KhisxJNaJPIToy0AtpyeJt690MVNctjeIVaLb2OrEI6250X0Vl3xGbNNSPn0UjazJNQww14D3Vo4EVlA/s1600/testi6.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="212" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiNdkyHQM4_whwzs1l9dDSuar1MRmdYDNigebod41KYL_9C8HcVZv42rrRle-2KhisxJNaJPIToy0AtpyeJt690MVNctjeIVaLb2OrEI6250X0Vl3xGbNNSPn0UjazJNQww14D3Vo4EVlA/s320/testi6.jpg" width="320" /></a></div><div class="separator" style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZYdPUjg4fs0948TzKSJqhZWgAYHMM4Ac63qmnlCx4zXl9o1wwNnlpN1Q3dpzkTRyV0GyLzXVD1-SaVo-aAnJxFfoxa4A-gz_i8hWrGiP80muBvRGDjlrpmkgAOLSc4nUIwWN8dJErfdA/s1600/testi9_Ha.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="214" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZYdPUjg4fs0948TzKSJqhZWgAYHMM4Ac63qmnlCx4zXl9o1wwNnlpN1Q3dpzkTRyV0GyLzXVD1-SaVo-aAnJxFfoxa4A-gz_i8hWrGiP80muBvRGDjlrpmkgAOLSc4nUIwWN8dJErfdA/s320/testi9_Ha.jpg" width="320" /></a></div><br />
Testing the imaging quality proved difficult to say the least. With nine points to adjust and some structural flexing focusing and collimation is almost impossible. Overall the system seems a bit soft and low contrast, but at least on H-alpha narrowband filters it gave a fairly good resolution on the focused area. Still, the high intensity regions bleed over darker ones reducing the contrast a bit too much. Additional baffling migh help keep the stray light away, but the glow around bright areas does indicate that high contrast isn't a priority for these lenses.Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-78919583608969681472011-05-21T12:42:00.001+03:002011-05-21T12:45:35.435+03:00Initial focus testing<div style="float: right; margin-left: 10px; margin-bottom: 10px;"><a href="http://www.flickr.com/photos/mickut/5740318213/" title="photo sharing"><img src="http://farm6.static.flickr.com/5310/5740318213_1b4ec3121a_m.jpg" alt="" style="border: solid 2px #000000;" /></a><br /><span style="font-size: 0.9em; margin-top: 0px;"><a href="http://www.flickr.com/photos/mickut/5740318213/">Initial focus testing</a><br />Originally uploaded by <a href="http://www.flickr.com/photos/mickut/">Mickut</a></span></div><i>Via Flickr:</i><br />I wish I had a DSLR with live view, it made focusing and testing a lot easier. At short focal lengths the image is soft and low contrast, so unfortunately the optics seem useless for a fats, widefield astrograph. I still have evaluate at a significantly longer FL to see is it any good as a planetary scope.<br clear="all" />Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-52334031358901849012011-05-21T12:38:00.001+03:002011-05-21T12:45:35.437+03:00Short and stout<div style="float: right; margin-left: 10px; margin-bottom: 10px;"><a href="http://www.flickr.com/photos/mickut/5740314637/" title="photo sharing"><img src="http://farm4.static.flickr.com/3615/5740314637_2254d71251_m.jpg" alt="" style="border: solid 2px #000000;" /></a><br /><span style="font-size: 0.9em; margin-top: 0px;"><a href="http://www.flickr.com/photos/mickut/5740314637/">Short and stout</a><br />Originally uploaded by <a href="http://www.flickr.com/photos/mickut/">Mickut</a></span></div><i>Via Flickr:</i><br />The telefocus optics keep the overall length very short compared to focal length. This rig is a major pain to collimate, but luckily its main purpose in life is to evaluate general usefulness of the lenses and the distances between flanges for a suitable focal length and sufficient back focus distance.<br clear="all" />Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0tag:blogger.com,1999:blog-7939836829441641427.post-32832600464818711002011-05-21T12:37:00.001+03:002011-05-21T12:45:35.439+03:00Assembled for testing<div style="float: right; margin-left: 10px; margin-bottom: 10px;"><a href="http://www.flickr.com/photos/mickut/5740862850/" title="photo sharing"><img src="http://farm6.static.flickr.com/5025/5740862850_12c4104625_m.jpg" alt="" style="border: solid 2px #000000;" /></a><br /><span style="font-size: 0.9em; margin-top: 0px;"><a href="http://www.flickr.com/photos/mickut/5740862850/">Assembled for testing</a><br />Originally uploaded by <a href="http://www.flickr.com/photos/mickut/">Mickut</a></span></div><br clear="all" />Anttihttp://www.blogger.com/profile/09733012746385551055noreply@blogger.com0