Didn't that hurt?
----- Original Message -----
From: "Craig Colvin" <tac@craigcolvin.com>
To: <jvn@svpal.org>; "The Astronomy Connection" <sf-bay-tac@seds.org>
Sent: Tuesday, July 27, 2004 2:52 PM
Subject: Re: [TAC] Exit Pupil size?
> 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 15:00:24 2004