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Ha measurements for the 1600 at gain200:
with a 6nm Ha filter and f4 optics, sampling at about 0.75arcsec.
measured dark sky in 10 minute sub = 11.7 photoelectrons
measured noise = 3.87 photelectrons rms
expected shot noise (from 11.7 photoelectrons) = 3.41 photoelectrons rms
read noise <1e rms
ie, even with subs as short as 10 minutes the shot noise of 3.41e is completely overwhelming the read noise of <1e under what was fairly dark sky - very much shorter subs could have been used without penalty. It would have been close to sky-noise limited even at gain 100, where the dynamic range is much better. For comparison, my H694 would not have been anywhere near sky-noise limited at 10 minutes, since it has read noise that is significantly higher than the measured shot noise
Also, the measured noise is a fraction of an electron higher than the combined shot noise (due to the signal) and the read noise - ie there is a smidgin of fixed pattern noise in there, but it is vanishingly small. This camera seems to work predictably right down to the theoretical limits.
The maximum useful sub length needed for Ha imaging with my system is around 10 minutes at gains of 100+ and shorter subs will do the job if the sky is bright.
Last edited by Shiraz; 18-10-2016 at 03:24 PM.
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