Eyepiece exit pupil question

Hi there !

For fun, hi checked the exit pupil of some of my eyepiece. I check this in
looking the eye-lens with holding the eyepiece at the end of my arm.

For some eyepiece the exit pupil is about 6 to 12 mm, (Speers Waler 7mm and
18mm, Nagler 12mm type 4) but for other eyepiece the exit pupil seems to be as
large as the eye-lens (Speer Walers 30mm, Omcom Erfle 52mm, Omcon Plossl 40mm).

What is that ?

Thanks and clear sky !

Hi there !

For fun, hi checked the exit pupil of some of my eyepiece. I check this in
looking the eye-lens with holding the eyepiece at the end of my arm.

The exit pupil is a function of the focal ratio of the scope being used and the
focal length of the eyepiece. Need to use a scope.

I think what you are looking at is the field stop which sets the Apparent Field
of View of the scope. The AFOV is approximately the field stop diameter
divided by the focal length of the eyepiece converted then from radians to
degrees. AFOV=(Field stop/focal length)*57.3 degrees

Thus the short focal length eyepieces have smaller diameter field stops and
when used without a scope an apparently smaller "exit pupil."

jon

"André P." wrote in message
...
Hi there !

For fun, hi checked the exit pupil of some of my eyepiece. I check this
in
looking the eye-lens with holding the eyepiece at the end of my arm.

For some eyepiece the exit pupil is about 6 to 12 mm, (Speers Waler 7mm
and
18mm, Nagler 12mm type 4) but for other eyepiece the exit pupil seems to
be as
large as the eye-lens (Speer Walers 30mm, Omcom Erfle 52mm, Omcon Plossl
40mm).

What is that ?

Thanks and clear sky !

You are not viewing the exit pupil. The exit pupil exists only when the
eyepiece is in the telescope.

Jon Isaacs wrote:
Hi there !

For fun, hi checked the exit pupil of some of my eyepiece. I check this in
looking the eye-lens with holding the eyepiece at the end of my arm.


The exit pupil is a function of the focal ratio of the scope being used and the
focal length of the eyepiece. Need to use a scope.


Thanks to you Jon !

Michael A. Covington wrote:



You are not viewing the exit pupil. The exit pupil exists only when the
eyepiece is in the telescope.


Thanks Michael !