How to determine binoculars focal lenght?

On 26 Aug 2003 13:36:33 +0200, "daysleeper" wrote:

Hi!
Is there a simple way to determine the focal lenght of the binocular
lense, without taking it apart?
I own 15 years old russian 20x60 Tento binoculars. Maybe some of you
know the FL of that one...
I guess it's around 400mm (F6.6), but I might be very wrong

Clear & steady skies!

Without taking it apart? I don't know how... But try to measure the light-path
from the objective to the ocular as precisely as you can. The difficult part is
to trace around the prisms correctly... The focal length is about 10mm less
than your measure.

Also, look at them carefully as most of the times it is easy to remove either
the objective or the ocular or both.
Benoît Morrissette