Tuesday, November 23, 2010

Interesting thought on night sky photography

Background: it's super hard to get sharp, bright photos of the night sky. With decent ISO and aperture, the exposures get long enough to cause the stars to streak across the picture. The professional approach would be to get a star tracking rig for $$$$, OR....

Take, say, 100 10-second exposures at high sensitivity, find the 2-d cross-correlation function between each pair of consecutive images (assuming you have nothing else in the FOV, or if so then mask it out), and shift and co-add them? If the noise is additive and normally distributed you can continue ad nauseum–the SNR is proportional to sqrt(N) where N is the number of integrations.

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