GALEX Exposure Time Calculator

The GALEX Exposure Time Calculator (ETC) is used to simulate the GALEX instrument response for observations of different types of astronomical objects (stars, galaxies, and QSOs). There are two calculation methods that can be used with the ETC. The first method is to specify an exposure time and the ETC will return the predicted signal-to-noise ratio (SNR). The second method is to specify an SNR and the ETC will return the exposure time needed to obtain it.

The user must specify the flux from the object being observed, either using a flux density or magnitude. The ETC does not use the input position to compute the flux of the object being observed. The input position is only used to compute an estimated background at the position of the object being observed. Options that can be used to more fully describe the object being observed are available from the 'Advanced' interface.

Interface Control: Basic / Advanced
Labels with the symbol are required.

Calculation Method
Input Method Type

Basic Interface assumes ƒ ν = constant and no Milky Way extinction.
Input magnitudes are assumed to be in the AB system.
Input fluxes/magnitudes are assumed to have no Milky Way extinction along the line of sight (details).
Input Flux Type


Coordinate System

decimal degrees DDD.DDD or sexagesimal HH MM SS.SSS

decimal degrees [+/-]DD.DDD or sexagesimal [+/-]DD MM SS.SSS
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