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Re: (meteorobs) spectacles and LM
On 2 Oct 2000, at 9:58, Joe Kaplonek wrote:
> 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?
>
>
No, no, no! Absolutely not. There is a common misconception
around that any optical aid, with greater physical "aperture" than
the human eye will help LM. That is only true if it magnifies. Any
unity magnification optical aid will not improve LM because the
ratio of aperture to exit pupil (iris) is equal to magnification, which
is 1. This follows directly from geometrical optics. To benefit from
increased aperture, magnification must be increased accordingly.
For example, to see one full magnitude fainter, your aperture must
be increased by 100^(1/5) in area, about 2.51 times. The diameter
must be sqrt(2.51) = 1.58 times greater. Thus, from geometrical
optics, you need a magnification of 1.58X to achieve this one
magnitude increase in LM. So bottom line, your spectacles have to
be magnifying spectacles to improve LM, not just be aberration
correcting!
Hope this helps clarify a slightly confusing subject...
Good unity mag observing!
Mike.
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