Quote:
Originally Posted by Shiraz
just tested another dataset with 16 very similar calibrated subs. the noise in a few subs chosen at random varied from 4.55 to 5.5 with a mean of about 5. A stack without any rejection produced a noise level of 1.24, which is almost exactly 1/4 of the average sub noise levels - as it should be for 16 subs. I am not seeing any gain at all over the expected sqrt(n) due to alignment before stacking.
ie, I get Stacknoise = Subnoise/sqrt(n)
A stack of the unaligned subs had noise about 25% higher than that from the aligned stack - assume that this indicates some residual FPN.
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That makes sense, Ray. Shot noise imposes an upper bound on SNR and the best you can do is minimise the effect of read noise, thermal current noise and FPN.