A possible problem exists if the user wants to take the output of this program (or take images combined as suggested by this program) and use SYNPHOT to convert the counts to flux units. The problem is that this program includes the attenuation effects of the pick-off mirror, but SYNPHOT also includes corrections for the (unpolarized) attenuation of the pick-off mirror. To remedy this situation, a correction can be applied to the output of this program by selecting "YES". The correction simply multiplies the results by the average (average of TE-mode and TM-mode) attenuation of the pick-off mirror.
Mosty users should select "YES" unless they have some specific reason to omit the correction.
-J. Biretta, STScI