function blackbody,L,T1,FAHRENHEIT=F,CELSIUS=celsius
;Planck's blackbody curve
;T is temperature in kelvins
;L is wavelength in meters

h=6.626e-34
c=3e8
k=1.38e-23

T= KEYWORD_SET(F) ? 0.555882*T1+255.312 : T1
T= KEYWORD_SET(celsius) ? T1-273.1 : T1
c1=h*c
c2=c1/k
c3=2*!pi*c1*c

Return,c3/(L^5*(exp(c2/T/L)-1))
end