This free tool is courtesy of the Madawaska Highlands Observatory.
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This tool is adapted from "Astronomical
Computing" Sky & Telescope, May 1998, ccdlimit.bas by Bradley
E. Schaefer, and converted to Java Script by Larry Bogan. Adapted
by The Madawaska Highlands Observatory to fit this console, with
filters changed to the u', g', r', i', z', used a more precise
sigma error calculation routine, added mirror/lens transmission
inputs, added total transmission output, changed the sky brightness
output to mag/arcsec² and rounded results for better presentation.
Also added to capability to calculate to a selected s/n ,sigma
value and calculate limiting magnitude to a preset exposure. All
values above the results be can changed to fit different conditions.
The results are good to within 0.2 magnitudes. A default degraded
sky is set 21.90 mag/arcsec² to more accurately reflect the
local sky conditions at the site, this can be changed or disabled.
Total system transmission is the net multiplication effect of
: quantum efficiency * mirror reflectivity (#filters) * lens transmission
(#lenses) * filter transmission.