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Hubble Space Telescope
Surface Brightness of Background Light

Input the surface brightness in magnitudes per square arcsecond.

The default is to use Johnson Visual magnitudes, but you can use the menu to select other Johnson-Cousins magnitudes, or AB magnitudes.

U, B, V, R, and I are standard magnitudes in the Johnson-Cousins system. (U, B, and V are from Johnson, and R and I are from Cousins. V and Visual magnitude are equivalent.) The table below is used to convert the input magnitudes to V before calculation:

Color                            Spectral Type
-----  ------------------------------------------------------------------------
       O5    B0   A0   F0   G0   G5  K0III  M0III   gE    Sa   Sbc   Scd   IrI
U-V  -1.43 -1.36 0.04 0.31 0.65 0.82  1.86  3.46   1.64  1.62  1.28  0.51  0.05
B-V  -0.30 -0.29 0.02 0.25 0.54 0.62  0.91  1.44   0.99  0.98  0.91  0.50  0.37
V-R  -0.14 -0.15 0.01 0.17 0.36 0.40  0.51  0.89   0.53  0.48  0.43  0.36  0.28
V-I  -0.31 -0.27 0.03 0.36 0.73 0.76  0.95  1.74   1.10  0.99  0.90  0.70  0.66

Stellar colors are from SYNPHOT runs using Bruzual synthetic spectra. Galaxy U-B and B-V colors are drawn from Longo and deVaucouleurs 1983 for representative objects;V-R and R-I are estimated from WFPC2 Handbook Table 6.1. Galaxy colors are probably accurate to only to ~20%.

AB_xxxxx are AB magnitudes at the standard WFPC2 filter bands. For example AB_F555W means AB at the effective wavelength of the F555W filter (5398 Angstroms). AB magnitudes are defined as:

AB = -2.5 log10(F(nu)) - 48.60

where F(nu) is the flux in erg sec-1 cm-2 Hz-1.

Band       Effective Wavelength (Ang.)
-------    ---------------------------
F160BW           1492
F218W            2192
F255W            2586
F300W            2943
F336W            3342
F439W            4300
F555W            5398
F675W            6696
F814W            7921
F1042M          10184