idlastro / Astronomical Utilities: PLANCK

[Source code]

NAME
PLANCK()   
PURPOSE
To calculate the Planck function in units of ergs/cm2/s/A  
CALLING SEQUENCE
bbflux = PLANCK( wave, temp) 
INPUT PARAMETERS
WAVE   Scalar or vector giving the wavelength(s) in **Angstroms**
        at which the Planck function is to be evaluated.
TEMP   Scalar giving the temperature of the planck function in degree K
OUTPUT PARAMETERS
BBFLUX - Scalar or vector giving the blackbody flux (i.e. !pi*Intensity)
        in erg/cm^2/s/A in at the specified wavelength points.
EXAMPLES
To calculate the blackbody flux at 30,000 K every 100 Angstroms between
2000A and 2900 A
IDL> wave = 2000 + findgen(10)*100
IDL> bbflux = planck(wave,30000)
If a star with a blackbody spectrum has a radius R, and distance,d, then
the flux at Earth in erg/cm^2/s/A will be bbflux*R^2/d^2
PROCEDURE
The wavelength data are converted to cm, and the Planck function
is calculated for each wavelength point. See Allen (1973), Astrophysical
Quantities, section 44 for more information.
NOTES
See the procedure planck_radiance.pro in 
ftp://origin.ssec.wisc.edu/pub/paulv/idl/Radiance/planck_radiance.pro
for computation of Planck radiance given wavenumber in cm-1 or  
wavelength in microns 
MODIFICATION HISTORY
Adapted from the IUE RDAF               August, 1989
Converted to IDL V5.0   W. Landsman   September 1997
Improve precision of constants    W. Landsman  January 2002