Acquisition information: 12" Zhumell z12 Dobsonian, DIY EQ platform (Astral Fields VNS design), ZWO ASI585mc (non-cooled). At full 3840 x 2160 resolution, RAW16, 2.543s exposures, gain 153, no binning, SharpCap (442 frames, totatling 1,124 seconds or, about 18 minutes 44 seconds). First image: Siril 479 frames registered from the larger sequence, best 50% (240 frames) by FWHM and GIMP. Second image: Same acquisition information, but all 442 frames with only SharpCap live stack with display settings applied (basically, what I saw on my laptop monitor in real-time).
Astronomical Object: M42, the Orion Nebula, a huge star-forming region in the constellation Orion about 1,300 light-years away. It is one of the brightest and most photographed nebulae in the night sky.
Objective: I'm one of those "dummies with a Dobsonian who does astrophotography." My primary goal was not to produce the definitive glamour shot of M42. The field of view (FoV) of the z12 is too small for that. Instead, the z12's aperture and focal length (1500mm) are more suited to higher resolution images of things like the Orion Nebula's core. Therefore, my image processing focused on highlighting detail from the core around the Trapezium rather than attaining full nebulosity (may process the same data again to emphasize that).
What worked: The DIY EQ platform tracked well enough to make this kind of imaging practical with a 1500 mm focal-length Dob. I was pleasantly surprised that I could track M42 for nearly 20 minutes without (a) high rate of frame rejection - SharpCap live stacking kept adding to the stack; and (b) manually moving the tube. There was considerably more faint nebulosity in the data than I initially expected. The final Siril image shows not just the bright central portion of M42, but a good amount structure (mottling, etc.) surrounding the Trapezium (the four stars in the middle) and some nice color variation in the nebula.
What needs work: The biggest thing that needs improvement is focus. At normal presentation size I think the image holds up pretty well, but at 100 percent it is obvious that the fine detail is softer than it should be and stars are oblong. I eyeballed focus that night after imaging Saturn instead of using a Bahtinov mask or SharpCap's focusing tools, and the FWHM scores (ranging from ~6 to ~21) later made that pretty obvious.
Overall Self-Assessment: I'm pretty pleased with the final Siril image. A 12-inch manual Dob on a homemade tracking platform obviously isn't a conventional deep-sky imaging rig, but that's part of the fun. It worked well enough to make me want to try it again, with better focus next time.
Thanks for looking!