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Re: (meteorobs) spectacles and LM
Kim,
I also had my contact lens and glasses' prescription updated at the
very same time (and this has been done more than once). Despite
identical prescriptions, I can assure you that glasses are NO match
whatsoever to contact lens. Although I've eliminated any possibility
of "poorly made" glasses for my eyes, stars always appear very
slightly out of focus. This effect is not evident at all under
daytime use. I get 20/20 or better with glasses in the daytime.
The problem of wearing glasses at night may be minor enough not to
bother most people but since I'm such a perfectionist about my
vision, it did to me! Testing this at night gave me a gain of as much
as 0.3 in extra limiting magnitude with contact lens compared to
glasses. This is significant in my opinion. Contact lens makes very
faint stars stand out more. Under good conditions, I can split
Epsilon Lyra quite easily with contacts, but this has never been
possible with glasses (looks more like a single elongated star)! I
would assume very faint meteors to be harder tough to spot through
glasses.
Oh, and without any glasses or contacts, my vision at infinity is
severely affected. I would probably have a tough time seeing a magn
+3 star under any condition.
I've asked a number of eye experts, and their explanation seem to be
that because contact lens are "closer" to the eye than glasses are,
tiny objects (like stars) look sharper and more accurate during
nighttime conditions. Could that make sense?
I now wear contacts for nearly all my observing. Another advantage is
no more worrying about glasses "fogging up" in the cold. I've never
lost any contact lens so far, but I always keep a kit with spare
glasses just in case! I also have extra containers and cleaning
solution in case I DO want to remove & store them when my eyes get
tired after several hours.
Pierre
Kim Youmans <ksyo@pinelanddot net> wrote...
>I can only speak for myself and my own experiences. Last year
>during the 99 Persieds, I had both my contact and glasses
>prescriptions updated at the same time. I performed the simple
>experiment of taking both contacts and glasses out to my observing
>site and counting the IMO fields with each. The contacts proved
>superior, but of course there was always the possibility of the
>glasses not being as well fitted to my eyes (prescription-wise) as
>the contacts. The glare was worse with the glasses and naturally I
>had complete peripheral vision with the contacts, unacheivable with
>the glasses.
> I don't think one can compare glasses to telescopes anymore
>or any less than one could compare contacts and telescopes. Glasses
>and contacts do exactly the same thing. We do have posters here (at
>least one, anyway) who are experienced observers and state that they
>have 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!
> 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!
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