Signal-to-noise calculator for CCD photometry

Apr 6, 2003: fixed minor error in calculation of flux inside small apertures
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.

Assumptions:

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.

Filter: This calculator uses Bessell filters, which are close to Johnson UBV, Cousins RI.
Mag Limits: List values for magnitudes between: and at intervals of mag.
Telescope diameter: (cm):
Overall QE: (0.0-1.0): primarily determined by CCD
Pixel size: (arcsec/pixel)
CCD readout noise: (electrons)
Sky brightness: (mag per sq. arcsec)
Airmass:
Exposure time: (seconds)
FWHM: (arcsec)
Radius for photometry: area over which signal is measured (arcsec):

You may have to wait 10-20 seconds for result.

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Last updated Aug 30, 2004 by Michael Richmond.