PRO lightcurve, w, t, f, lc, dm ;; extract lightcurve from 2d spectra


;; Input
;
;  w      wavelength array
;  t      timing array
;  f      2d spectra f(w,t)
;
;; Output
;  lc     light curve F(t),  where F = Int[ f(w)dw ]
;  dm     light curve in differential magnitudes
;
;;


nw = n_elements(w)
nt = n_elements(t)

                                     ;; trapezoidal integration
lc = fltarr(nt)
lc = 0.
FOR iw = 0,nw-2 DO BEGIN
  lc = lc + ( w(iw+1)-w(iw) ) * ( f(iw,*)+f(iw+1,*) ) / 2.
ENDFOR

lc = lc / ( w(nw-1) - w(0) )         ;; normalize integral

dm = 2.5 * alog10 ( lc / mean (lc ) ) ;; convert to differntial magnitudes

END