The Great Orion Nebula (M42) and Equipment Tuning

My objectives tonight were pretty much the same as last night, which were to get a good calibration and decent guiding in PHD, and to get plate solving and autofocus working in NINA, and to take a series of test exposures to see to what exposure duration that tight, round stars hold up.

The seeing this evening was fantastic, but it would been a horrible night for imaging because of a constant parade of high thin clouds. This was, however, a fantastic night for the work that I had in mind.

The temps were in the low 40s and RH was 70% when I went out to power up and polar align at about 1830. The sky was completely clear, but soon high clouds started drifting through. The temperature was 35 degrees and the RH had risen to 72% by the time I completed the session at 2100. There was frost on the telescope cover, but no dew or frost on anything else.

I had let myself get a little chilly before going out to change the mount from the GM8 to the G11, and I didn’t dress warmly enough for going outside to do this work. Because of this, I got horribly cold in a short amount of time. I had to come inside to warm up.  I put on a heavier jacket, and was fine for the rest of the change over, and for the considerable amount of time I spent scope-side while working out issues.

There was nothing noteworthy about the PoleMaster polar alignment. The symbology in the monitor mode was steady, which indicated good seeing. Calibration completed with our error and the graph looked pretty good. I stepped into Guiding Assistant for three minutes. The polar alignment error was 4.2”, and I let that stand without going to Drift alignment. I could see that seeing was pretty good because the high-frequency star motion values were low. The backlash chart looked great. I accepted the GA recommendations, and stepped into guiding.

Dec RMS was .30 to .35” which was fantastic. Ra RMS was probably good enough at .90 to .95”, but I was certain that the huge difference between the Ra and Dec RMS would cause elongated stars, and I was right.

Plate solving worked flawlessly the first time.

I struggled with autofocus. I was working off script because it was cold, and that led to me forgetting to check the focus knob clutch. I finally figured it out and was getting perfect focus results.

I loaded M42 in the sequencer, allowed NINA plate solving to go find it and center it, autofocus the camera, start guiding, and take some test exposures.

I found 20s in L and 30s each in RGB to be optimal from a histogram perspective. I want to be able to expose longer to minimize frame numbers, storage load, and processing load, so I did a series of 30s, 60s, 120s, and 240s exposures. I found that I started seeing elongated stars at 120s.

Ra guiding was the biggest deficiency that I had tonight, but I did not work on it. I’ll read on it tomorrow and work on it in my next session. I have a dark dust mote, probably on the camera front glass, because it is visible no matter what filter is in place. I can probably Flat it out, but I’d rather this one be gone.

M42 - 2022-12-29 02:55 UTC
The Great Orion Nebula (M42)

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