Why can GALEX observe bright stars? What are the brightness limits?
Fundamental detector safety requirements limit observations of bright targets. Currently, point sources, with flat spectra, may not be observed (imaging or grism) that are brighter than: mAB = 9.5 or Fn = 0.6 Jy or Fl = 7 x 10-12 erg cm-2 s-1 -1 in the FUV; mAB = 10.8 or Fn = 0.2 Jy or Fl = 1 x 10-12 erg cm-2 s-1 -1 in the NUV. Bright and / or crowded fields may not be observed if they exceed total brightness levels of : (65000 counts / sec) = Fn = 7.8 Jy or Fl = 9 x 10-11 erg cm-2 s-1 -1 in the FUV; Fn = 2.6 Jy or Fl = 1.5 x 10-11 erg cm-2 s-1 -1 in the NUV. Pointing centers must be separated from bright stars by : 0.75o for an object with Fl = 1 x 10-12 erg cm-2 s-1 -1, or mAB = 10.8 (NUV, ~ 2300 ) (5000cts/s) 0.88o for an object with Fl = 1 x 10-11 erg cm-2 s-1 -1, or mAB = 8.3 (50,000cts/s) 1.00o for an object with Fl = 4 x 10-11 erg cm-2 s-1 -1, or mAB = 6.8 (200,000cts/s) 1.50o for an object with Fl = 1 x 10-10 erg cm-2 s-1 -1, or mAB = 5.8 (500,000cts/s) 2.00o for an object with
