Via Flickr:
Thick, 27mm plywood for the main lens, thinner 10mm ones for negative lens and camera mount. Four holes will be drilled into each, three for threaded rods and a big one at the center for optics.
2011-05-19
2011-05-18
Astrograph project starts
My mystery optics order from Surplus Shed of a very fast air spaced triplet and negative doublet arrived today. The weight is a bit of a concern, the triplet lens (D=155mm, f/1.23) weighs a whopping 2.5 kg and creating a stable focusable system for these two is going to be challenging. The smaller, but not lesser, negative doublet weighs "only" 414 grams, and is unmounted, edges painted black with elements glued together. I took a chance on these, as the big lens for half off, and at a total price well below 200€ shipping, taxes and customs included wasn't too bad if these can be combined to even a reasonably good fl=465mm f/3 astrograph. Since I'd use mainly narrow band filters with it, I'm not too concerned about color aberrations, mainly about the image plane flatness for the fair size CCD sensor in SXVR-H18.
The next step is to create a temporary rig for determining correct spacing between elements in order to reach the desired focal lenght, the thin lens equations say it's in the order of 150-160 mm, but this is now the real world. In theory short test exposures should be doable with it as well before creating the actual tube assembly.
The structure for the OTA served a challenge, as the back focal distance from the negative element to image plane at infinity focus is fairly short, in the order of 80 millimeters at desired focal length. This leaves out the option of building a rigid tube and attaching a commercial focuser at the back, but I realized I might just be able to construct a Huge Crayford focuser and put the optics into the inner tube and attach the camera to the outer tube, eating only 15-20 millimeters of the focus travel. As a result the final tube would end up around 20cm diameter and 20cm long looking more like a snare drum than a telescope, but who cares.
The next step is to create a temporary rig for determining correct spacing between elements in order to reach the desired focal lenght, the thin lens equations say it's in the order of 150-160 mm, but this is now the real world. In theory short test exposures should be doable with it as well before creating the actual tube assembly.
The structure for the OTA served a challenge, as the back focal distance from the negative element to image plane at infinity focus is fairly short, in the order of 80 millimeters at desired focal length. This leaves out the option of building a rigid tube and attaching a commercial focuser at the back, but I realized I might just be able to construct a Huge Crayford focuser and put the optics into the inner tube and attach the camera to the outer tube, eating only 15-20 millimeters of the focus travel. As a result the final tube would end up around 20cm diameter and 20cm long looking more like a snare drum than a telescope, but who cares.
2011-02-15
The Great Orion Nebula narrowband
January 2010 version of M-42
I've learned a few things over the fairly short period I've been trying to do astrophotography, here's the ever-so-cool M42 with my current capabilities. As a comparison, side-by-side from January 2010 and February 2011 the same target. Naturally, part of the difference comes from changes in equiment used, the 2010 was shot on a Canon 350D thru an el-cheapo achromatic fl=1000mm f/10 refractor with racket-and-pinion manual focuser seated on tripod-mounter HEQ5 mount and no guiding. For the 2011 version I used Starlight Xpress SXVR-H18 CCD-camera, high-quality Baader filters, guided exposures with dithering and for optics I have now access to the astro-club's William-Options 110-FLT on pier-installed EQ6 mount.
Many small changes a small change in image makes. Oh, and the image on left was taken at nearly new moon, and the newer version is 70% full moon glaring right above Orion.
2010-11-29
NGC7000 - LBN354
Oh well. If it can fail, it will fail.
Not sure if anything went smoothly tonight, first I went almost off-the-road then got nearly stuck on the hill to the imaging site. When there, the scope shelter was buried in a foot of snow and the locks were frozen. Finally I got almost everything assembled, simply to realize that the power-cord from the transformer to 12V distribution block was left home. Luckily I found one in the nearly warm cabin, so it was time to fire up the gear. Velcro glues peeled off the mount in the -20 temperatures, and I had to fetch a rope to tie the distribution block to the mount. Quite soon it was obvious that nothing worked perfectly, so park the scope, dis- and reconnect all wires, restart applications and everything seems to work nicely for a change. Except, when focusing I noticed that the shutter isn't fully open on all of the frames. Tried a few longer exposures and the same thing continued, the upper half was more likely to go all the way off-sensor, lower half got stuck one third the way down. In six hours I managed to get 30 minutes of botched luminosity instead of targeted 3+ hours of LRGB data.
Not sure if anything went smoothly tonight, first I went almost off-the-road then got nearly stuck on the hill to the imaging site. When there, the scope shelter was buried in a foot of snow and the locks were frozen. Finally I got almost everything assembled, simply to realize that the power-cord from the transformer to 12V distribution block was left home. Luckily I found one in the nearly warm cabin, so it was time to fire up the gear. Velcro glues peeled off the mount in the -20 temperatures, and I had to fetch a rope to tie the distribution block to the mount. Quite soon it was obvious that nothing worked perfectly, so park the scope, dis- and reconnect all wires, restart applications and everything seems to work nicely for a change. Except, when focusing I noticed that the shutter isn't fully open on all of the frames. Tried a few longer exposures and the same thing continued, the upper half was more likely to go all the way off-sensor, lower half got stuck one third the way down. In six hours I managed to get 30 minutes of botched luminosity instead of targeted 3+ hours of LRGB data.
2010-11-17
Slow progress is still progress
My simplistic SW-project for automating the tedious task to center on a target is slowly bearing fruit. At last I have a GUI written that can be used to test whether my library works correctly or not.
The current capabilities of the GUI are capturing an image (at least screenshot, ASCOM and from file works), solving it with astrometry.net -solver, syncing and reslewing an ASCOM compatible telescope, and calculating the distance from assumed target and solved image center.
I'm still not decided on the name, currently the library is AstroMate and the preliminary name of the GUI is AstroTortilla. Hopefully I end up with a single name, although the second utility based on the same library is an alignment helper (currently unstarted and unnamed) based on automatic imaging and solving when moving on the RA axis.
I'm still not decided on the name, currently the library is AstroMate and the preliminary name of the GUI is AstroTortilla. Hopefully I end up with a single name, although the second utility based on the same library is an alignment helper (currently unstarted and unnamed) based on automatic imaging and solving when moving on the RA axis.
2010-11-14
The end of a season
Yestarday was the end-of-season party at the golf club, featuring a fairly funny comedian trickster who had a couple of new tricks up his sleeve, but mostly his definitely well practiced quips on people and events around made an impression. This year I didn't succeed on any of the competitions, so hopefully I get to practice a bit during the winter and early spring in order to improve my game come next summer. This season was definitely "ruined" by the short game. On the Hill course I reached the green from tee five times, and on 15th three times, didn't score a single eagle. What's even worse is that out of those eight chances for an eagle I made only two birdies. Anyone willing to go practice with me, just to make sure that practicing would happen?
2010-11-10
Blog relocation
I've relocated my old blog(s) here from Wordpress and MovableType, and it was almost a straight forward conversion using the google-blog-converters-appengine web-services. Only some minor issues like character encoding didn't auto-convert to UTF-8 so that had to be done by hand, and one of the blog-posts had an eight-dash line which in MovableType export file marks the end of a blog-entry. This caused the XML to be malformed and the entry importing froze without indication of error.
All in all this should now be my real blog, some old entries are likely broken, especially the ones trying to show images in pop-up windows.
All in all this should now be my real blog, some old entries are likely broken, especially the ones trying to show images in pop-up windows.
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