Apr 6, 2003: fixed minor error in calculation of flux inside
Mar 2, 2004: fixed another error in calculation of flux inside very small apertures
Aug 30, 2004: now PSF centered on a pixel, rather than split at junction of 4 pixels
This form allows you to calculate the signal-to-noise ratio for a star observed with a telescope and CCD. You can vary the parameters and find out what sort of results to expect.
If you want to see the calculations themselves, try reading the Perl source code to the calculator. Or, if you just want to see the equations governing the calculations, try this article by Steve Howell.
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Last updated Aug 30, 2004 by Michael Richmond.