Getting started with an ASI2600MC-P camera, as a significant upgrade from a DSLR. I've got it working, but wonder if there are a better set of settings that I should be using.
My scope is a Stellarvue SVA130EDT, unreduced, so it's running f/7. The mount is an AVX, so I generally used fairly short subs (20-30 seconds) with my Nikon D3200 DSLR, even with it under autoguider control, running the ISO up to 3200+ to compensate. That put the histogram at about the 1/4 point, as reported on the back of the camera. I'm in Bortle zone 6+ here.
First real images were this past week. The acquisition software platform is CCDciel + INDI on a 4gb Raspberry Pi-4B. A 10 second test exposure at a gain of 100 (it's described optimal value) and an offset of 5 (chosen by me, to keep a Dark from having a lot of zero pixels) netted absolutely nothing. Bumping the gain to 300, and a 60 second exposure seemed usable, if still a little dim. The histogram (as displayed in CCDciel) wasn't off the left edge yet, but there was a little hint of a tail starting. I grabbed the Goofi Challenge image there. With that "in the can", I tried 4 minutes exposure. Seemed a lot better with the histogram, and I went off to pick up M33. The mount cooperated for some reason, and I got some good subs. (See M33, below.) I'm using a 2x2 on-camera Bin for all of this, in order to improve download time, and because it should improve SNR. I'd bin in processing anyway, and doing it on-camera means I get more net imaging time.
Looking at the settings in INDI, there are a number of defaults under "Controls" that I don't know what optimal values should be. These are my questions for this thread.
1. The Offset interacts with the Gain setting. Is there any magic about what to pick, as long as I'm not picking something so large as to saturate things? Is 5 ok? Too small?
2. Color balance. There are settings for Red and Blue, which are defaulted to 52 and 95, respectively. My skills in color balance are close to nil; are there better choices here? StarTools 1.6 doesn't have an "Identity" setting for astro cameras in the color module, so that's not going to save me.
3. I know I'm eating into the dynamic range by picking a gain of 300. The INDI default was 200, and ZWO says that 100 is the optimal value. Given that I don't want to run 12 minute subs (even 4 minutes is historically unrealistic), is there any other way to get a bit more sensitivity out of the camera? What is the "best practice" setting for Gain and Offset on this camera, when used with an f/7 telescope? Or, am I ok with the histogram pushed up against the left margin, given that the histogram thing is a rule of thumb for DSLRs, and this isn't a DSLR?
4. Format. Choices are Raw 8 bit, RGB 24, Luma, and Raw 16 bit. Raw 16 bit is the default, and what I used, but I'm wondering about RGB24. What's that used for and is it better? I'm using DSS for stacking, and StarTools for processing, if that matters. I did end up with a color image.
5. I've got the temperature set to -5C. Seems to work... Any significant reason to go lower? I run from batteries, and the current draw increases the colder you get. According to Robin Glover's video, in Bortle 6 it should hardly matter to even be cooled.
6. The AntiDewHeater is set to 0. What should be set here, if it's needed? How would I know? Is this a % of max type of setting?
7. Calibration subs. Some cameras work well with Bias, some don't and prefer Darks. I grabbed a set of both, but which calibration strategy should I be using for this camera?
8. Anything else I should be considering?
Below is a "test image" of M33, cropped only a little around the edges for stacking artifacts. Just 46 minutes total integration, with most of the subs taken at 4 minutes, 300 gain, 5 offset. Stacked in DSS, quickly processed in StarTools. I think it's a lot better than what I submitted from the DSLR back in October 2018. There's also the submission to the Goofi Challenge of NGC-7129, as another reference.