The card works for both!
----- Original Message -----
From: "P T Chambers" <ptchamb@svpal.org>
To: <jvn@svpal.org>; "The Astronomy Connection" <sf-bay-tac@seds.org>
Sent: Tuesday, July 27, 2004 2:16 PM
Subject: Re: [TAC] Exit Pupil size?
> 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 14:59:07 2004