Gain and noise in solar imaging
Posted: Tue Oct 19, 2021 11:06 am
I know that this has been discussed before but here goes again
up until now when I am imaging with my ASI174mm I keep the gain at 150 and then adjust gamma, 1-4 for surface and up to 100 for proms, normally on proms I run it about 95-100 but often do extra runs at 90 or whatever gives me a darker sky but doesn't lose much if any of the proms I set the speed to get the exposure I want, usually running 15 or 20 milliseconds and 50 or 60 fps for the surface and up to 50 milliseconds or higher and 25 or 30 fps for proms.
I usually shoot 500 frames for a prom and stack 25 or 50 of them (mostly 50 frames stacked), sometimes will go 1000 frames on a prom but not often. For the surface I shoot 1,000 or 2,000 frames once in a while more and again stack about 50 or sometimes 100 frames.
I seem to get good exposures and low noise.
On CN, yes CN and their gurus, they are saying you should set your milliseconds to no more than 10 ms and they often or usually use 4 milliseconds (MS) and then adjust the gain for the exposure they want and DON'T use gamma at all. Sharpcap 4 doesn't have gamma so you don't have a choice I use Sharpcap 3. They also are saying only do one exposure, that for the surface and try to pull the proms out in post processing.
First I have found that with two exposures one for the surface and one for the proms, I get better results on the proms.
The last two days I did a test, on Sunday I used 10 MS for everything and then on Monday I used 4 MS for everything. I had to run my gain up around 300 for the proms and in the low 200's for the surface.
I then compared the stacked images from Autostakkert of the proms against images I took with 150 or less gain. The results as I expected from my time as a professional photographer and current published Nature Photographer, is the higher the gain (or ISO on cameras) the MORE NOISE (grain).
The more noise the less detail!
It is an unscientific test, just comparing by eye, but to me shooting at 4 to 10 ms and high gain has more noise.
I seem to remember that John never shoots over 30 fps, what does everyone shoot at? milliseconds/gain/ frames per second?
up until now when I am imaging with my ASI174mm I keep the gain at 150 and then adjust gamma, 1-4 for surface and up to 100 for proms, normally on proms I run it about 95-100 but often do extra runs at 90 or whatever gives me a darker sky but doesn't lose much if any of the proms I set the speed to get the exposure I want, usually running 15 or 20 milliseconds and 50 or 60 fps for the surface and up to 50 milliseconds or higher and 25 or 30 fps for proms.
I usually shoot 500 frames for a prom and stack 25 or 50 of them (mostly 50 frames stacked), sometimes will go 1000 frames on a prom but not often. For the surface I shoot 1,000 or 2,000 frames once in a while more and again stack about 50 or sometimes 100 frames.
I seem to get good exposures and low noise.
On CN, yes CN and their gurus, they are saying you should set your milliseconds to no more than 10 ms and they often or usually use 4 milliseconds (MS) and then adjust the gain for the exposure they want and DON'T use gamma at all. Sharpcap 4 doesn't have gamma so you don't have a choice I use Sharpcap 3. They also are saying only do one exposure, that for the surface and try to pull the proms out in post processing.
First I have found that with two exposures one for the surface and one for the proms, I get better results on the proms.
The last two days I did a test, on Sunday I used 10 MS for everything and then on Monday I used 4 MS for everything. I had to run my gain up around 300 for the proms and in the low 200's for the surface.
I then compared the stacked images from Autostakkert of the proms against images I took with 150 or less gain. The results as I expected from my time as a professional photographer and current published Nature Photographer, is the higher the gain (or ISO on cameras) the MORE NOISE (grain).
The more noise the less detail!
It is an unscientific test, just comparing by eye, but to me shooting at 4 to 10 ms and high gain has more noise.
I seem to remember that John never shoots over 30 fps, what does everyone shoot at? milliseconds/gain/ frames per second?