Quote:
Originally Posted by ericwbenson
Unless the resampling loses resolution it cannot gain SNR, otherwise it gains information for free.
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However, I'm pretty sure that resampling does lose resolution, so you don't get anything for free!
For example, take a single pixel star on the original sub and resample at 0.5px in x and y. It would get smeared over surrounding pixels.
On the other hand, if the pixels in the original sub were of a uniform background, it's exactly this smearing effect that reduces the noise and improves SNR.
I think, that the lose of resolution in stacking will often explain why stack FWHM is usually less than individual sub FWHM.