idlastro / Astronomical Utilities: FLUX2MAG

[Source code]

NAME
FLUX2MAG
PURPOSE
Convert from flux (ergs/s/cm^2/A) to magnitudes.
EXPLANATION
Use MAG2FLUX() for the opposite direction.
CALLING SEQUENCE
mag = flux2mag( flux, [ zero_pt, ABwave=  ] )
INPUTS
flux - scalar or vector flux vector, in erg cm-2 s-1 A-1
OPTIONAL INPUT
zero_pt - scalar giving the zero point level of the magnitude.
          If not supplied then zero_pt = 21.1 (Code et al 1976)
          Ignored if the ABwave keyword is supplied
OPTIONAL KEYWORD INPUT
ABwave - wavelength scalar or vector in Angstroms.   If supplied, then 
      FLUX2MAG() returns Oke AB magnitudes (Oke & Gunn 1983, ApJ, 266,
      713).
OUTPUT
mag - magnitude vector.   If the ABwave keyword is set then mag
      is given by the expression 
      ABMAG = -2.5*alog10(f) - 5*alog10(ABwave) - 2.406 
      Otherwise, mag is given by the expression  
      mag = -2.5*alog10(flux) - zero_pt
EXAMPLE
Suppose one is given wavelength and flux vectors, w (in Angstroms) and 
f (in erg cm-2 s-1 A-1).   Plot the spectrum in AB magnitudes
IDL> plot, w, flux2mag(f,ABwave = w), /nozero
REVISION HISTORY
Written    J. Hill        STX Co.       1988
Converted to IDL V5.0   W. Landsman   September 1997
Added ABwave keyword    W. Landsman   September 1998
efault zero pt