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Re: (meteorobs) spectacles and LM

>Question:  If a telescope >>>extends visual limiting magnitude, wouldn't
>glasses (spectacles) do the same thing and actually be beneficial in
>helping >>>observe fainter meteors?  Regards,Joe. **

Stronger glasses do allow observing of fainter meteors, but not for the same
reason a telescope extends LM.  The telescope is gathering more light, and
you assure proper focus by adjusting the eyepiece holder accordingly.  For
naked-eye watching the stronger glasses give sharper focus so that fainter
point objects can be seen.  Blur the faintest stars into little globes,
their light spreads out over a larger area, thus the surface brightness of
the blob falls below your detection limit.  If two objects, a star and a
nebula, have the same magnitude, the star is more easily seen with all the
light concentrated into a point and able to stimulate a single rod receptor.


>glasses which are -if I recall correctly - a diopter stronger than
>necessary - yet their present *meteor* perception doesn't seem to be
>anything extraordinary.  Their LM perception, on the other hand, does
>appear quite a bit better than average.  Help me out here, Norm!

An extra diopter would pull your eyes out of your head.  A quarter extra
diopter is enough.  At night the pupil dilates, thus leaving your day
glasses undercorrecting slightly.  I achieve the same effect by lifting the
glasses up off my ears, thus slightly rotating the lenses and getting a
stronger correction.  It would be better to get stronger night glasses made.
Only problem is the very high cost of frames.  They are priced as though
they are made of platinum.


>        I have to wonder, however, about the health aspects of using
>glasses that are too strong over extended periods.  It may be perfectly
>OK -- I'm no opthamalogist!

Seems like no problem if not exceeding the quarter diopter.  You couldn't
stand much stronger correction for long.

I visited an optometrist at Walmart recently and had a glasses upgrade.
Right eye needed to be strengthened a little.  The optometrist was impressed
with my eye health at my present age of 54.  He decided dilation with drops
wasn't necessary since my pupils were already large enough for him to see
inside.  And I again read the 20/10 line with glasses on -- he seldom has
someone able to do that.

With large lenses there should be little loss of meteors in the periphery.
No one sees a large number of meteors beyond 50 degrees from central vision
anyway, except for those with the highest perception.  Moisture on the
inside of the lenses on a still night is a minor problem -- I have to take
them off and wave them around for a few seconds. And there are occasional
stray light flashes from bright stars, planets, airplanes, or cars -- learn
to mentally filter these out.  My limit without glasses is still around 6.5,
not all that bad.  And I have occasionally seen a 5th-magnitude meteor
without the glasses.  But there's a big difference between 6.5 and 7.4 so I
have to wear them..

Norman


Norman W. McLeod III
Staff Advisor
American Meteor Society

Fort Myers, Florida
nmcleod@peganet.com

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