CCD v CMOS

[Gina]

50 minutes ago, kens said:

60dB gain (gain 600) is way too high. You have less than 4 stops of dynamic range there. I keep the gain at 200 (20dB) or lower where the dynamic range is a bit less than 10 stops.

Typically I use gain 75 for luminance,  139 (unity) for RGB and 200 for narrowband unless I an get a reasonable exposure at 139.

In the past I got some good results with a gain of 600, such as the Barnard's Loop et al I posted earlier in this thread but I think I'll do some experiments with lower gain next time we get clear night sky.  As I recall, I did experiment a bit with the gain and found the higher the gain the better but it probably also depends on image processing.

Edited October 5, 2019 by Gina

[Adam J]

36 minutes ago, Gina said:

In the past I got some good results with a gain of 600, such as the Barnard's Loop et al I posted earlier in this thread but I think I'll do some experiments with lower gain next time we get clear night sky.  As I recall, I did experiment a bit with the gain and found the higher the gain the better but it probably also depends on image processing.

Gain 600 really is way too high, no benefit I am aware of beyond gain 200 with the ASI1600mm pro.

Adam

[david_taurus83]

I'm also having a hankering for trying out a CCD. I got my ASI1600 a year ago and it's been very pleasing after starting with a DSLR. However, I tend to go against the grain of all the short sub hype and shoot much longer subs. Currently 900s with an Ha 7nm. I tried 20 minutes the once and it was even smoother than the 15 minutes but I didn't want to shoot another set of darks at the time. Also, I shoot RGB at around 3/5 minutes. I tried 30s subs the once and it was a bit of a pain to pre process and I messed up the last few hundred subs because of a wrong gain setting!

Been thinking about an Atik 460 as it still has smallish pixels and a decent sensor size. Should still cover a lot of objects with my GT71 at 336mm.

 

So, has anyone started mono with a CMOS and then made the switch to CCD and never looked back? Or has anyone regretted going CCD and switched to/back to CMOS with no regrets? (I couldn't justify keeping both, the ASI would have to go to fund the Atik)

[andrew s]

In my view using two CCD cameras and one CMOS with the right technique you can make either perform to a very high level. It is easy to forget that modern CCD and CMOS chips are miles ahead of those just a few years ago. 

I doubt either your  current CMOS camera or the proposed CCD will limit what you can achieve. 

Regards Andrew 

[jimjam11]

3 hours ago, kens said:

60dB gain (gain 600) is way too high. You have less than 4 stops of dynamic range there. I keep the gain at 200 (20dB) or lower where the dynamic range is a bit less than 10 stops.

Typically I use gain 75 for luminance,  139 (unity) for RGB and 200 for narrowband unless I an get a reasonable exposure at 139.

I do similar, I use 76 for LRGB and 200 for narrowband. I get 30s L, 60s RGB and 300s for Narrowband. I then interleave the frames in SGPro so I capture LRGBL before a dither...

[Thalestris24]

Hi Gina

I have a qhy183m cmos camera. Compared to either my Atik383l+ ccd or my qhy8l osc ccd, it's much more sensitive, less noisy and much quicker to download images. But both ccds have bigger pixels and are 16 bit, so much greater well depth, plus can do proper binning, of course. You can look at the graphs of gain v dynamic range/well depth and noise. There is an optimum (not sure what it is for the asi1600). I generally find I get better (=nicer) images if I keep the gain very low on the 183 as dynamic range falls off pretty rapidly with increased gain. However, I'll wack up the gain to aid focusing and platesolving then reduce it back to the low value for actual imaging. The 183m is low noise and high QE (84% I think) - not sure how that compares to the 1600.  I have to admit I was quite sceptical about cmos cameras because of them being only 12 bit but my one can still produce quite nice images - as everyone else's cooled cmos cameras do too, of course!

Louise

[alan potts]

A tad off topic but I have a 183MC and whilst I saw amp glow (or at least I think it's that) on the 3 minute Darks that I shot at minus 5, I have not seen any on the stacked data and I had a good look for it. I will be the first to admit I don't have much of an idea how to use any of these things but just follow advice people are kind enough to offer. I actually feel it takes decent shots.

Alan