; file: planck.pro = Planck function
; last: Nov 19 1999

function planck,temp,wav
; computes Planck function in erg / cm2 sec [delta lambda = 1 cm] ster
; input: temp = temperature (K)
; wav = wavelength in cm

; physics constants in cgs (all cm)
k=1.380658D-16        ; Boltzmann constant (erg K; double precision)
h=6.626076D-27        ; Planck constant (erg s)
c=2.997929D10          ; velocity of light (cm/s)

;wavcm=wav*1E-4        ; change wav in um into cm
;wavcm=wav*1E-8        ; change wav in A into cm
wavcm = wav
blambda = 2*h*c^2/(wavcm^5*(exp(h*c/(wavcm*k*temp))-1))
;blambda=blambda*1E-4  ; change B_lambda into per micron
;blambda=blambda*1E-8  ; change B_lambda into per Angstrom

return,blambda
end