Re: ATM Exit Pupils & Big Scopes

[Bob Luffel <bobl@gr.hp.com>]

> 
> On 8/14/96 2:55PM, in message <960814.150056.CDT.CCMEG@MIZZOU1>, "M.E. 
> Germann" <CCMEG@MIZZOU1.missouri.edu> wrote:
> 
> > For those embarking on big projects it might be useful to
> > know your own personal entrance pupil. . .and what it is
> > likely to do (change) over the next decade or so.
> 
> How about some insight as to how to measure and then extrapolate change 
> with age?
> --
> Regards,
> JIM FLY
> jfly@HIWAAY.net
> 
> 



I was recently looking into this myself (how to measure your entrance pupil).
I have the Sky & Tel pupil gauge.  According to this gauge, my pupils
(at age 38) dialate to 5mm.  However, I also measured using my telescope and
various eyepieces.

I have an f/7 scope (ratio pretty accurate).  Basically, I pointed my
scope at a bright star and defocused the image so I could see the scope's
exit pupil size.  With a 40mm eyepiece the exit pupil should be 5.7mm.  I could
just fit the whole exit pupil (large image of the star) into my pupil without
cutting any of it off.  By this method, I estimate my pupil to be ~ 6mm.

This disagrees with the Sky&Tel gauge by quite an amount.  I wonder if the
method I used with my telescope has some flaw in it, or if the Sky&Tel
approach is just too coarse to measure accurately.  I would be interested
in hearing others' methods for measuring entrance pupils.





Bob Luffel