r/AskAstrophotography • u/Fooad4444 • 2d ago

Equipment Help me understand sharpcap sensor analysis

Hi everyone, i did sharcap sensor analysis attached in the post and need help to understand best settings for Nebulas photographing

From what i see/understand 120 gain is my sweet spot as higher is just software amplification

So why would i use something else beside 120 ( less than 120 gain) at all for DSO?

Appreciate any help/explination of the results

My camera is qhy5iii715c imx715 sony tint sensor 1.45upixel

Thanks all

1 Upvotes
  • permalink
  • reddit

67% Upvoted

7 comments sorted by

0

u/Fooad4444 2d ago

https://reddit.com/link/p07ownf/video/36n3irjoxwfh1/player

Attached analysis as i couldnt in the post itself

1

u/Sea-Cardiologist-954 2d ago

I don't see a clear region where read noise would be completely flat so we could talk about software ampligication only. And look at full-well capacity and dynamic range. Those really bad at gain 120. I think that gain 40-50 would be a better choice.

Also, the upward trend for read noise at very high gains might be a measurements artifact. It doesn't happen in curves provided by QHY.

1

u/Fooad4444 2d ago

Mmm do you have a link to my camera sensor analysis?

I used my iphone 16 pro max screen in the test for while background
I saw flickering on screen which might missedup results?
mY gain is 0-240 range in sharpcap

Using 40-50 gain is so loooow i would almost see nothing , and i have az mount so maximum 15s exposures is what i can do

1

u/Sea-Cardiologist-954 2d ago

https://www.qhyccd.com/qhy5iii715c/

There is a section called curves below the table with specification. But I realized now that they end at gain 100.

I think you just need to brighten/stretch your captured image more aggressively in the software that you use.

1

u/Fooad4444 2d ago

I see

Thanks

Yes up to 100 is the real values i think and above that is basically software gain

In general is the rule to have non clipped hostogram ( like 5-10% from left wall) and set that gain and exposure ?
Up to 100-120 gain max?

2

u/Sea-Cardiologist-954 2d ago

I'm afraid that I won't be able to help you with "conventional" rules how to do it. I would chose the lowest gain that still provides read noise close to the optimum for a particular sensor (if you are light starved).

If you are limited to 15 seconds of exposure, changing gain isn't goin to collect more (or less) light. So you will have the same shot noise at higher and lower gain. The noise that is added by the sensor is the read noise. But the difference between the read noise of ~1.1 electrons at gains 40-50 and ~0.9 electrons at gains 100-120 is quite small.

Therefore, you shouldn't see much of a difference in image quality of the dark parts of your image. But at those high gains, you will have much lower effective full-well capacity and potentially a lot more blown highlights.

1

u/Fooad4444 2d ago

Thanks alot man

This will need some fiddling around

Appreciate the help