Subject: Normalizing binned fluxes


  Dear friends,

  as you may remember one of the things we want to update for the
detector spectra and lightcurves is to also normalize them to
cts / 100 cm^2. Following a more eXtreme approach, this can be
broken down into two steps, for both I have some questions to
the team:

1. The trivial solution

   Calculate used area (in cm^2) as circle.

   For non-imaging data:
     area = full area  = pi *(12.5cm)^2

     Q1: shouldn't we have that area as constant somewhere (e.g. jemx.h)?

   For imaging data:
     area = pi * radius_limit[cm]^2 


2. The elaborate solution:

   For non-imaging data:
     As above. No way to correct.

   For imaging data:
     Calculate area based on the effective pixel sizes of those pixels 
     where events matching the GTI/STATUS/... selections could have been 
     found.

     Q2: How does one correctly obtain that area?  
         One cannot just use the events since sometimes there may be
         pixel positions which could have been hit but weren't for a
         given dataset.
         Should we try to define a function calculating the effective
         area based on radiusLimit and the event selections?


  Your inputs are very welcome,
  Peter