Flux Calibration

The technique most frequently used to flux calibrate a spectrum is to re-use the standard source which has a known brightness quoted relative to Vega ( Lyrae is defined to have zero magnitude at every wavelength). The flux density, , of a star at magnitude m can be described thus (Puxley 1988, Mountain 1985):

The software uses the values of flux densities for Lyrae that are listed in table and automatically accounts for the exposure times of source and standard.

When the flux standard is also the ratio-ing source, in equation is known and we immediately obtain a flux calibrated spectrum. If the flux and spectral standards are not the same then one must determine the relative brightness of the two stars by flux calibrating the spectral standard.

  
Table: Flux Densities for Lyrae