I see there are 2 interpretations of the question. One set thinks that
Mark wanted to measure how big his pupil gets.
The other set thinks that he wanted to measure the actual -exit pupil- of
an EP/Scope combination.
OK, Mark, inquiring minds want to know.... Which is it ???? LOL
---------
Phil Chambers [ptchamb@svpal.org] (S.F. Bay Area - Calif. USA)
On Tue, 27 Jul 2004, Jim Van Nuland wrote:
> Mark Wagner wrote:
> >
> > Is there such thing as a pupilometer, so I can measure the
> > size of my exit pupil?
>
> I use a caliper. Point the scope & eyepiece at the daytime sky or
> lighted ceiling. Stand behind the eyepiece with both eyes open, about a
> foot or two back, and you'll see a tiny light disk, floating just above
> the eye lens. With a bit of practice, you'll find that you can hold the
> caliper at just the right distance. Adjust it in steps of 0.1 mm or so,
> and you'll find that you can measure the image.
>
> OTOH -- if you know the actual focal lengths of primary and eyepiece,
> divide the eyepiece focal length by the f/ratio of the primary. Or
> divide the diameter of the primary by the magnification.
>
>
> OR -- did you mean to measure the pupil of your eyeball?? I'd call
> that your eye pupil, or entrance pupil, maybe.
>
> Cut a strip of paper about 300 mm long, tapered from about 12 mm wide
> to about 3 or 4 mm wide. Set up a small point source a few meters away.
> Put on your eye patch. Darken the room. Wait a while. Hold the paper
> strip vertically before your observing eye, and move it up and down
> until you *just* lose the point of light. It'll take some practice; as
> you move your head side to side, you'll see the light past each edge of
> the paper. What you want is to lose the light for the smallest instant;
> if the paper is too wide, you'll have a range over which the light is
> lost; too narrow and you won't lose it at all. When you believe you
> have the correct position, CAREFULLY mark the paper with a pencil, at
> your eye's pupil. Do it over a few times. At last, turn on your red
> light and see if the pencil marks are consistent. If so, measure the
> width at that spot.
>
> One of the secrets of a well-known SJAA comet hunter is that his
> dark-adapted eye has a 10 (ten) mm pupil!
>
> --
> Jim Van Nuland, San Jose (California) Astronomical Association
> JVN's home page
>
>
Received on Tue Jul 27 14:20:23 2004