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there was little diifference between a stack of 1000 x2.5sec exposures (integrations) and a stack of 200x2.5 sec exposures
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Well, there will be a difference because the former has 5 times the integration time. When comparing many short vs few long subs, it all comes down to the read noise of the camera. With no read noise, 1000 x 1 sec is identical to 1 x 1000 sec or 10 x 100 sec, in terms of signal-to-noise ratio (where noise in this case is shot noise). But with read noise to account for, the longer subs are better. But if you want statistical removal of artifacts, you'll typically want 10+ subs - and as you use more, the 'return on investment' diminishes with the square root of the number of subs.