Modified webcam gain adjustment

[Kaptain Klevtsov]

Excellent stuff. I hadn't got round to playing with the gamma yet. I now don't need to mess about for as long trying to get the thing to work as well as it should. Thanks Robin, all good stuff.

Captain Chaos

[robin_astro]

Hi Martin,

Thanks for the link I will take a look at that.

OK I have had a look at the calculator there

http://www.ccdware.com/resources/subexposure.cfm

and I think I can see what they are doing.

The sky background photons also produce shot noise. Once this noise becomes significantly greater than the read noise, (ie the image is sky noise limited) there is no longer a significant disdavantage to taking a series of sub exposures of this length and summing them. The end result will not be significantly worse than a single long exposure and of course taking a series of subs has many practical advantages.

It should be possible to simulate the same effect with my spreadheet by increasing the camera thermal noise (which has the same characteristics as sky background noise). The percentage deterioration in signal/noise in going from a single exposure to an equivalent length stack should reduce

Robin

[MartinB]

Thanks Robin. I think I was misregurtitating what I have been reading. I thought that the shot noise would effectively be reduced by combining but this obviously isn't the case. Having said that I have been using a celestron fastar system and skyglow develops very quickly with that so my exposures will still be limited.

[CELESCOPE]

Blimey this is a long thread ehhehheheh , well CC as you know all my images with the 2hs have come out pretty well , i,m a bit late on replying , seems a lot of interesting answers from everyone , but this is how i done it , DSOs i started off with the gain at 50% ,this seemed to be a happy setting , but remember i was using Faststar, at f1.95 .so 45 to 1 min exposures . so the gain at 50% suited me,

amp off was used , but i dont think amp glow came in before 40 secs anyway , subs needed were at least 45 to 50 , to settle any noise levels , but i must say that Maxim is a great bit of software that i used , and any other noise was cleared up using Noels actions , Planets i tend to up the gain , , massive stacking can then rid most noise , so thats it DSO 50% gain Planets about 75 %, i personally think its down to what equipment you have and working to get the best results ,

Rog