I would say Exit pupil = Objective diameter / Magnification , which makes Relative Brightness Index = square of ( objective diameter / magnification). > For satellite observation (and general astronomy > observation) I've been using the "Relative Brightness > Index" as the measure for rating a binocular's ability > to gather light. This index is defined as the exit > pupil diameter divided by the magnification and > multiplied by the objective diameter. > > For 7x50s the index is 51 > For 10x50s the index is 25 > For 12x50s the index is 17 > For 7x35s the index is 25 > For 20x60s the index is 9 > ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www2.satellite.eu.org/seesat/seesatindex.html
This archive was generated by hypermail 2b29 : Thu Apr 12 2001 - 05:15:56 PDT