FOV Binoculars
If you have a pair of binoculars some manufacturers will indicate the field of view by marking somewhere on the frame..xxx@1000 feet..if it is marked 235@1000 it means if you looked at a 235 foot ruler 1000 feet away it would stretch completely across your field of view.
Author and Astronomer Phil Harrington in his book 'Touring the Universe Through Binoculars' has a formula to determine the FOV in degrees based on that manufacturers mark. Divide the xxx value by 52.5...my 10x50 were marked 235@1000 so 235/52.5 = 4.51 degrees...
To test the formula I went out last night and found a pair of stars, Mizar and Alioth inthe handle of the Big Dipper, that are approximately 4.5 degrees apart. There was a star on each side of the field just as predicted..
Now I can star hop using my binoculars...
BTW I the used ECUlite4 star chart program to find a pair of stars 4.5 degrees apart for the test. It has a feature that can measure angular distances between stars on the chart.
Phil Harringtons book 'Touring the Universe Through Binoculars' has an excellent chapter on binoculars and how to choose a pair.
Ok Lets get out there...The mosquitoes are waiting...
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