I have done the same thing using metric allen wrenches.
-Craig
...... Original Message .......
On Tue, 27 Jul 2004 14:07:59 -0700 Jim Van Nuland <jvn@svpal.org> 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 14:52:25 2004