Two steps forward, one step sideways.

December 18-19.

Three small steps today. The play in the SBIG connection turns out to be from a worn / cheap-ass T-mount adapter. I swapped the one I had been using for another in the parts drawer. The connection became much firmer. Maybe I'll eventually add an actual, honest to goodness new one to the kit.

As I was pushing and prodding on the micrometer focusing adapter for the refractor, I snapped it clean off its bracket. Apparently JB Weld can be pretty brittle if the proportions are not just right. We'll call that "destructive testing of the prototype" and regard this as my cue to make a proper adapter. I have a lathe, and I have a milling attachment, and I have a nice long, soft aluminum tube of exactly the right diameter and wall thickness. Bluff called. Model B will be smaller, more secure, and have 50% less reduction. Stay tuned.

The shorter USB cables are here and in place. The electronics ride much less tangliferously, which is to say that when looking behind the telescope there is less reason to think of Spanish moss. I had to swap two USB slots in order to use 12-inch rather than 18-inch cables, which meant I had to reinstall a bunch of drivers. Go figure. I expected this, so did it by daylight to avoid squandering darkness.

In the dark. Guiding: If you get "guide star not found," do an auto-dark. Noise is probably confusing the guider in the absence of a really conspicuous guide star.

When I began, the weather was too warm to get the chip to -35C. I began exposing at -33.8C and 100% cooling. I didn't expect Maxim to calibrate these early frames using my -35C darks, but had no problem getting it do so. When the ambient temperature dropped to the low 50'sF, the chip finally reached the setpoint (e.g.: 52F, 96% cooling, -34.9C). One hour in, the images look pretty good. Then in the 90 minute frame, the telescope suddenly lurched 10-20 pixels in both axes as if a cat had leaped on it. The guider took 210s to recover; I lost two 10-minute frames in the process. Tracking is good again, but I'm not sure polar alignment remains good. What the hell? Anyway, I want two hours of data on M33 before going on to another target tonight, so there'll be plenty of information to examine.

I only got 110 minutes before something started acting up with tracking. Small guider corrections but smeared images. This can only be due to slippage somewhere in the CCD imaging train. Anyway. On to M82.

Messier 81 and 82 were exactly behind the peak of the house. The two could not have been placed any worse, given the position of the telescope. I entertained myself with a quick look at M42. Shot some 30 second frames and a couple of 5 minute frames. We'll try it for real eventually.

I finally got the telescope aimed at M81 and M82. The first composition was a little tight on M81. I didn't want to truncate those beautiful spiral arms. And two of my first three 10 minute exposures trailed. So I went outside, shifted the frame just a little to get some more room for M81, clamped everything down; then had a terrible time getting tracking restarted. But did. Dark frame, longer exposure, expose, specify the guide star, calibrate, track. I'm doing 7 second guide exposures. It appears from Guide 8.0 that the brightest star in my guide field is magnitude 10.4. Stars appear in much shorter frames, but I can't convince Maxim to guide on one.

The results of a single 10 minute exposure are pretty gratifying. The results of combining a few frames are even better. Tomorrow I'll hope to combine several. It's all I can do to keep my eye out for dew and other calamities.

At 110 minutes --again!-- I called it a night. There was a film of dew on the guider and probably as much on the main instrument. It could only get worse if I tried for 150 minutes and I figured a few additional images would be worth less than extra sleep.

The combined image doesn't look that different from the first ten minutes' image except that to pull up the outer spiral arms from the short exposure produces a fantastically grainy sky and an overblown core. In the summed and averaged versions of the best eleven frames, warped appendages at the ends of M82 appear, as does a hint of the streamers radiating from the core of M82, and so does a faint companion beside M81 at the 3-4 o'clock position (this may be a large starcloud far out in one of the big spiral arms rather than a seperate galaxy).

If I'm going to push the dynamic range of images as hard as I am pushing these tonight, then I need to calibrate with flats as well as darks. Might as well start building a library of standard and master flats, darks, and bias frames. Maybe that will minimize the need to spend the rest of my natural life collecting data to keep platteauing from marring the edges of my galactic suburbs. But first, sleep.

M33, The Pinwheel Galaxy,
quick look with data collection still going on.
80 minutes, 8x600s, averaged,
A-P 5" F6,
Clear IR blocked filter, ST2000XM @ -35C.

 

The Great Orion Nebula, M42.
1x30s + 1x300s,
a really quick look while waiting for M81 & M82.

 

M81 and M82, two galaxies in Ursa Major.
11x600s, Clear-IR blocked.
Averaged, summed, remixed. Larger versions
may show what's in there. Very tough processing,
these bright-cored galaxies.

 

 

 

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Text & Photos by David Cortner
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