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Improving Signal to Noise Ratio
Just after some clarification of improving SNR by stacking images (as an average, median or sigma combine method, not adding).
I've noticed some marathon imaging recently. One was 48 x 5min subs through a one shot colour camera.
From what I've read in Ron Wodaski's book, the "additional exposures improve the SNR by the square root of the number of exposures".
Thus,
4 exposures improves SNR by a factor of 2
9 exposures improves SNR by a factor of 3
16 exposures improves SNR by a factor of 4 etc...
There is obviously a diminshing return to any improvement to SNR by taking more and more subs. To me it just reduces precious time available to image other objects.
I've been taking between 10 & 15 subs as a compromise between quantity and quality. What do others do?
Has anyone shown a visible improvement from 15 vs 30+ subs?
Regards
David T
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