SXT_ERG_PER_DN returns the log of the radiative energy per DN
assuming a coronal spectral model with temperature, 
. The units
of the result are 
(erg/DN), where DN is assumed to be the
decompressed and background subtracted value that is read out of the CCD
camera. Example calling statements are:
IDL> log10_erg_dn = sxt_erg_per_dn(log10_Te,filter)
IDL> log10_erg_dn = sxt_erg_per_dn(log10_Te,filter,date='1-dec-92')
and 
and 
are input variables which may be vectors. is
the log of the electron temperature (K), of the solar plasma and
is the SXT filter number. For example, to compute 
(erg/DN) for all filters
over the range of temperatures between 
between 5.5 and 8.0 use the
following calling sequence:
IDL> Te = 5.5 + findgen(26)*.1 ; Generate a temperature vector
IDL> log10_erg_dn = sxt_erg_per_dn(Te,indgen(6)+1)
The purpose of the 
keyword option is to allow the post-November
1992 SXT response functions to be used. This can be invoked by specifying
any date later than ``14-Nov-92'', the day after a hole in the entrance
filter appeared, and caused the SXT response function to change.