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edcannon
professor emeritus
Reged: 11/19/03
Posts: 679
Loc: Austin, Texas
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Re: What does the 'Visibility Index' tell you?
01/04/07 02:58 AM
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Footnote - Alan Adler's index (magnification times square root of aperture) is pretty good for comparing binoculars of equal quality - of equal quality - (repeated for emphasis).
However, to my knowledge Ed Zarenski's is the only performance index for binoculars that attempts to figure in the importance of the optical quality of the binoculars being compared. If you are attempting to compare binoculars of different optical quality, use EdZ's performance index!
Footnote - for reference, a copy of Alan Adler's article is here:
http://www.weatherman.com/binadler.htm
Its biggest weakness may be underemphasis of coatings (a significant aspect of optical quality).
A couple of nights ago I had my Orion Ultraview 8x42 and compared the view with the $30 uncoated 10x42 roof, specifically to notice the glare from the Moon (when looking near but not at the Moon). The fully multicoated Ultraview crushed the uncoated 10x42 in that circumstance. Optical quality really does matter - of course.
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Ed Cannon - Austin, Texas, USA
As of 23 August 2008 - Celestron Skymaster 12x60
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