NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Off Center Sextant Scope Observations
From: George Huxtable
Date: 2007 Nov 24, 22:14 -0000
From: George Huxtable
Date: 2007 Nov 24, 22:14 -0000
Fred Hebard wrote- | As I recall when determining index error using the sun, the point of | contact varies with up and down location in the telescope. ================== Response from George. How interesting! When Fred says "As I recall ...", is he going just by a dim recollection, or is it a real, reproducible effect, that he can see whenever he tries to repeat it? To me, it appears to defeat the laws of optics as I understand them, but that doesn't lead me to deny that Fred saw what he saw. It makes it worth examining more closely to discover why. Could it result, perhaps, from a mirror that wasn't exactly flat, so the reflection angle varies slightly when you use a different part? Or a shade with a bit of ripple in it? Tell us more, Fred. George. contact George Huxtable at george@huxtable.u-net.com or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---