"Mike Jenkins" wrote in message
thlink.net...
About 6 weeks ago I purchased a pair of Leupold 10x50 binocs. This means
that these binocs have an exit pupil of 5. Right? The problem with these
is
the field of view is smaller than what I'd like.

I've been reading that as one gets older, the pupil doesn't dilate like
it
used to. I'm 47.5 years of age. Have I reached that point?

I ask this because I'm considering buying some binocs(used) with a wider
fov. I'm considering 7x50, 8x40, 7x42 and 8x56( maybe you folks have
better
suggestions).

Will the 7x50's and the 8x56's have too large of an exit pupil. My
thinking
is for astronomy, the more light the better. Is this thinking correct?.
How
will having too large of an exit pupil affect my astronomy observing? I
know the 7x50's and the 8x56's have an exit pupil of 7.1 and 7. Is this
too
large an exit pupil?

Would I be better of with 7x35's instead of 7x50's? 8x40's instead of
8x56's? Help!

Mike,

You can measure your exit pupil when you are dark adapted. Make a long
strip of light cardboard (a manila folder works well) that tapers from 2mm
wide to 8mm wide. While looking at a star, place the narrow end of the stip
in front of your eye, as close to your pupil as possible. You should see
the star on each side of the stip. Slowly slide it so the thickness is
increasing. When the star blinks out on both sides of the strip, that width
is your exit pupil. If the star vanishes from only one side, it is not
quite centered in front of your eye. Try again.

Having said that, you may need to get a pair of binoculars with a larger
than needed exit pupil to get a wide field of view. I bought a pair of
7x42s with an 8 degree field knowing I will probably not use the entire
aperture, and will never use it during the day. (They had other features I
could not find on anything smaller too.) Actually, if you look around,
there are some with a smaller exit pupil that have a reasonably wide field.
The Nikon Venurer 8x32s and the Swarovski 8x30 SLCs come to mind, and the
Nikon 8x32 Superior Es have a pretty wide field too, I believe.

Clear skies, Alan