Very nice start Rob. You should have a bit of fun with the camera. I do like the Leo triplet image, it has come up very nicely for such short exposures and only 3.
The only thing I would sugest is that you go to Craig Starks web site and read his directions on setting the gain and offset for any camera. After reading his explanation you may want to reduce the Gain figure a little bit.
Taken from the Nebulosity owners manual, but it is relevant for whichever software you use. Bare in mind the well depth of the QHY9 is 25.5Ke.
How to set Gain and Offset then forget it.
The best value for your camera may not be the best value for other cameras. In particular,
different makers set things up differently. For example, on a Meade DSI III that I recently tested,
running the gain full-out at 100% let it just hit full well at 65,535 ADU. Running below 100%
and it hit full-well at 40,000 or 30,000, or 10,000 ADU. There's no point in running this camera
at anything less than 100% gain. On a CCD Labs Q8-HR I have, even at gains of 0 and 1 (on its
0-63 scale), the camera would hit 65535 on bright objects (like the ceiling above my desk).
There's no point in running this camera at gains higher than 0 or 1.
Why is there no point? The camera only holds 25k e-. If a gain of 0 or 1 gets me to 0.38 e-/ADU
(so that those 25k e- become 65535), running at 0.1 e-/ADU will only serve to limit my dynamic
range. Each single electron already comes out to more than 2 ADU.
So, to determine the gain and offset to use:
1) Take a bias frame and look for the minimum value in it. Is it at least, say 100 and less than a
thousand or a few thousand? If so, your offset is fine. If it's too low, boost the offset. If it's high,
drop it. Repeat until you have a bias frame with an offset in, roughly 100 - 1000. Don't worry
about precision here as it won't matter at all in the end. You now know your offset. Set it and
forget it. Never change it.
2) Aim the camera at something bright or just put it on your desk with no lens or lenscap on and
take a picture. Look at the max value in the image. Is it well below 65k? If so, boost the gain. Is
it at 65k? If so drop the gain. Now, if you're on a real target (daylight ones are great for this) you
can look at the histogram and see the bunching up at the top end as the camera is hitting fullwell.
Having that bunch-up roughly at 65,535 plus or minus a bit is where you want to be. If you
pull up just shy, you'll get the "most out of your chip" but you'll also have non-linearity up there.
You've got more of a chance of having odd color casts on saturated areas, for example, as a
result. If you let that just clip off, you've lost a touch but what you've lost is very non-linear data
anyway (all this assumes, BTW, an ABG chip which all of these cams in question are). Record
that gain and set it and forget it. Never change it.
By doing this simple, daytime, two-step process you've set things up perfectly. You'll be sure to
never hit the evil of zero and you'll be making your chip's dynamic range fit best into the 16-bits
of your ADC. Again, all the cameras in question have full-well capacities below 65,535 so you
are sure to have enough ADUs to fit every electron you record into its own intensity value.
Good luck with it all and have fun. Very nice start.