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every good frame helps Logan - the "diminishing returns" argument was fashionable for a while, but was wrong.
Adding excessively noisy frames (eg from a moonlit night) does not help, since the added noise overwhelms the benefit of the added signal - as a rough rule of thumb, a few subs with sky background greater than about 2x the level of the bulk of the subs will do more harm than good. If that is all you have though, use them.
doubling the sky background increases the noise by 1.4, but the signal remains the same, so the SNR is down by a factor of 1/1.4. The only way to get it back up is by extra integration - which adds more sky noise and dark noise..... If a dim galaxy takes 10 hours to a reasonable SNR under M21 sky, it will take ~25 hours to get the same result under an M19 sky. Sky brightness is a killer and the only way to defeat it is more integration.
Last edited by Shiraz; 21-10-2017 at 12:28 PM.
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