Signal to noise ratio and gain

[cuivenion]

Hi, I'm using a GPCAM colour to take DSO images. I'm wondering how to set the gain. For my first couple of attempts I've used maximum gain in order to make sure that I picked something up, but I'm wondering if this is the best way to go about it. How do you think I should go about setting the gain on this cam in order to get the best signal to noise ratio?

Here's a couple of links to my first attempts with this cam:

 

[cuivenion]

Put this up quite late so I'll give it a cheeky bump.

[cjdawson]

I think your gain is fine where it is.  No harm in lowering it a bit if you want.  But by far the most important thing is take more sub frames and stack them.

When you get into it, you'll be wanting to take sets of lights, darks, flats and bias. All work together to bring more signal.

[cuivenion]

5 minutes ago, cjdawson said:

I think your gain is fine where it is.  No harm in lowering it a bit if you want.  But by far the most important thing is take more sub frames and stack them.

When you get into it, you'll be wanting to take sets of lights, darks, flats and bias. All work together to bring more signal.

Thanks for the reply, I think for the fainter targets max gain will be fine But I'll drop it for bright globs like M13. I tried a couple of test shots with a 50mm guide scope and M13 seemed to have it core blown out at max gain.

[cjdawson]

That sounds about right.  The lower the gain, the lower the noise from the chip.  Actually thinking about this, you could simply lower the gain for everything, then bring out the detail in post.  The key thing is that you are capturing the raw data rather than a jpeg or other format that losses fidelity.    I use a DSLR and image using Raw because the data in the raw file is the values that were read directly from the chip without any kind of processing.  It means that when I import the raw file to photoshop, all the data is then bought into memory and I can stretch the image to bring out the detail.  With Jpeg, the streching would stretch the jpeg artifacts and would degrade the image quicker.

[cuivenion]

Sounds like I have some experimenting to do. I capture in RAW, so I don't have to worry about that. I've been using darks, the light frames are very noisy without them.