Ernest A. Martsching wrote:

I'm wondering how difficult it is to calculate the field of view for my
binoculars and finder scope.
The binoculars are a pair of ProOptic 11x70 and an old pair of Jason 10x50
and the finder is an 8x50.
I'd like to plug those values into my planetarium program.
Thanks in advance.

Usually, many binoculars are stamped with the field in the form of the number
of feet wide the view is at a set distance like 1000 yards. For example, my
old 10x50's are 356 feet at 1000 yards (3,000 feet). To a fair approximation,
take half with width of the field and divide it by the range figure (3000 feet
in the case of many American binos), then take the inverse tangent of that
number and multiply it by two. That should give you the field in degrees. My
old Traq 10x50's have a field of about 7 degrees (lousy outer field quality),
and my new Celestron 10x60's have a field of 5.3 degrees (very sharp). Clear
skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

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