NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Douglas Denny
Date: 2010 Sep 26, 10:41 -0700
George:
...so I conclude that it is indeed very weakly astigmatic..
However, even my "good eye" isn't up-to-much these
days; it's due to get a session of retinal lasering tomorrow.
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Hmmm. I should have thought it was likely to be an astigmatiser lens, but very weakly astigmatic will not spread the star image out at all if placed on the eyepiece; it will however had a definite effect if it is placed in front of the objective of a telescope.
I took out my lens case to try it, to find the suitable amount of cylindrical power to use with a sextant telescope. Even just a half dioptre lens in front of the objective makes a nice small line with the laser spot on the wall across my living room. Nothing seen with the eyepiece of course.
Are you sure it is for the eyepiece or will it fit the objective? Some older telescopes have the same continuous diameter tube front end and back.
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Sorry about the eye problem, I sincerely hope all goes well for you.
Douglas Denny.
Chichester. England.
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