photons
      flux  f  =  0.08  ------------
                         s * sq.cm.


  Q:  How long will it take to collect N = 3.8 x 10^7 photons
            with a telescope of diameter 1 m?   10 m?


                           D = 1 m                  D = 10 m
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 Area (sq.cm.)            7.85 x 10^3              7.85 x 10^5

 Rate (photon/s)              625                   62,500

 Exptime for N (s)         60,800                      608
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