Quote:
Originally Posted by Stonius
I always find this confusing. for the 1600, RN is listed as 1.2e @30dB gain.
I assume this doesn't mean 'Gain setting 30' because according to the graphs in the manual, the gain units are in units of 0.1dB. So dividing by 10 can I assume that 300 Gain is 30dB and the magical point at which read noise is referenced to 1.2e?
As mentioned, it varies by gain, but I'm not sure how to calculate it for *other gains. I'd rather calculate it exactly rather than read values off those hokey little graphs but I don't know how.
Markus
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Working through your example and just going by the graphs, I get 141 at unity (offset 21) and 368 for Gain 200 (offset 50) for a ZWO1600.
On my test images of 47 Tuc I was getting the background around 2800 (16bit values) on Luminance subs of 30 secs at Gain 75, -20 degrees Celsius. I can't remember the offset I think it was 21. Maybe that's all wrong. The brightest parts of the image are at around 32,000. Statistics show the brightest pixels at 65504, just 31 shy of clipping at 65535. I think this was the basis on which I was exposing, TBH - not clipping, rather than skyglow)
It was a heavily light polluted area. Maybe I should have been using gain 200 with shorter exposures.
Markus