Kevin_A Maybe you can test out 150, Unity and HCG and see what your thoughts are.
I just measured two sets of dark frames at -10ºC. One set is at Unity gain, and the second set is at HCG gain.
When I compare the HCG (at half the exposure time of the Unity gain, to equalize the exposure value) with Unity gain, the HCG definitely has lower standard deviation (a.k.a. RMS). Not by much, but definitely there.
The dark current noise is still very dominant -- i.e., you can see the noise rise with exposure time (read noise should be constant with exposure time -- one read per exposure).
This is just one noisy camera for long exposures.
From that result, I think I will try HCG tonight with 100 sec exposure. Also abandon the Antlia RGB and use the Baader Neodymium instead. Moon is going to be nasty -- with more than 60% illuminated (the neodymium might help a little).
The HCG gain also has slightly better dynamic range than gain 150.
I'm taking some -10ºC dark frames at gain 252 and exposure 100 seconds right now to prepare for tonight. I still don't have dark and bias for last night's Unity gain and 180 sec. So, can't process those yet.
Right now, I am not sure it is worth getting the smaller pixels vs using the ASI2600. I can always teleextend the FSQ-85 by 1.5x for the larger 2600 pixels -- slows it down to an f/8 though. I think the 585 is just a cheap cooled camera - better than nothing, but not competitive with the better sensors.
BTW, does it irritate you that the long edge of the sensor, relative to the USB connectors, is 90 degrees from the ASI2600 orientation. No adult supervision.
Chen
