I am very new to CCD-style imaging, and I am using the new ASI071MC-Cool (Color) camera with the Sony IMX071 sensor.
Coming from a DSLR background, terms like Gain, Offset, ADU and debayering are new to me.
Well, first...as a DSLR user, you should be familiar with all of these things, except maybe offset. Gain is basically the same as ISO on a DSLR. ISO is really just the user-controllable way of changing gain with a DSLR. You can think of Gain on the ASI071 as a very finely-tunable ISO setting. Same basic deal.
You should also be very familiar with debayering. DSLR RAW images must be debayered before they can be used, however the same care must be taken with DSLR RAW as with ASI071 fits data. You MUST calibrate the data in either case before you debayer (also called demosaicing). Some tools may handle this for you, such as DSS. With DSS, you just need to set a bayer pattern when integrating FITS data for it to debayer for you.
DSLR cameras also have an offset. It is usually a fixed offset. In the case of Canon cameras, it is usually 512 ADU and on some newer Nikons it is 600 (ADU, Analog to Digital Units, the numeric range that the camera ADC outputs. Currently the vast majority of DSLRs and mirrorless cameras are 14-bit, so the numeric range is 0 - (214-1), or 0-16383. Many older Nikons don't use a bias offset, which results in clipped data. This is not a user-configurable option on a DSLR, however it is there. With the ASI071, it's just another user-configurable options much like ISO. To start, you should stick with the default ASCOM driver settings for gain and offset, and you won't really have to worry about either.
The issue I am having is the color balance of my stacked images coming out of DeepSkyStacker.
I have set the RAW/FITS Settings to the bayer pattern listed by the camera (In SGP settings): RGGB.
There was a previous thread about GBRG being the correct bayer pattern to use, but in my tests that was not the case.
The GBRG stack came out extremely purple and could not be corrected. (Skip to end of video)
The RGGB bayer pattern seems to work best, but the final image color is off. It has a greenish cast and is generally pale. Is not possilbe to balance the levels in PS afterwards either.
The RGGB pattern is indeed correct. I, too, have a very strong green color cast. I think that is in part due to the LP (low and high pressure sodium and mercury lighting can lead to greenish gradients) and also in part to the natural sensitivity of the green pixels in this particular sensor (the sensitivity of the green pixel to a fair amount of the NIR range is quite high and broad, which unfiltered can cause an even stronger green color cast). The color cast is most definitely correctable, however. You must properly remove the gradient (in PI, you would use DynamicBackgroundExtraction), and then you must properly neutralize the background and calibrate the white point (you can use PS with some basic layers or curves adjustments to neutralize the background, and eXcalibrator to calibrate the white point to G2V; alternatively in PI you could use BackgroundNeutralization and ColorCalibration to calibrate the color, possibly followed up by SCNR to nuke any remaining color cast).
Notes: I am shooting in (red zone) with no filters. Darks only, no flats or bias. (Still learning how to use the camera, and do not own filters)
I believe this camera is sensitive to the NIR range, so no filter at all could be problematic, both from a color standpoint as well as from a star bloat standpoint. While I am not a big fan of LP filters these days (I find they are all problematic in one way or another), you will likely need to use a UV cutoff filter or an L filter of some kind to prevent issues with IR light. You might want to consider a filter like this:
To make sure you are passing only the visible spectrum. Most LP filters will also suffice as a cutoff filter. I recommend the IDAS LPS-D1 for this camera if you want to use an LP filter.
I am using SGP for image acquisition using a various exposure lengths and Gain/Offset values. The camera was not cooled - as I do not have an external power source for the camera yet, but was used in -1 degree C weather.
I understand that I can improve the data immensely by using a LP filter and adding flats, but I feel like the color issue is something different.
If anyone has any experience with the ASI071MC-Cool (Color) I would greatly appreciate your input! I am happy to elaborate on any details if it helps diagnose the issue.
Attached is the best I could process out of the data aquired.
Since you are in a red zone, I would start out using the preset low gain (highest dynamic range) setting in the ASCOM driver for this camera. That will set the gain and offset properly, you won't have to worry about them, and it will give you maximum dynamic range. In a red zone, even at this setting, you'll likely only be able to expose for at most a couple of minutes, and by the time you do your read noise will be more than sufficiently swamped.
I have found that this camera does need flats, regardless of the lens or scope I use with it. It always seems to have a bit of vignetting, and I'm not exactly sure why, but flats definitely clean it up. Having a flat field is important to being able to properly calibrate the color and stretch the image without running into other issues.