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Re: Sextants with Polarizing filters
From: Fred Hebard
Date: 2006 Feb 7, 01:07 -0500
From: Fred Hebard
Date: 2006 Feb 7, 01:07 -0500
On Feb 7, 2006, at 12:45 AM, Frank Reed wrote: > Fred, you wrote: > "The one polarizing-shade sextant with which I have worked had > noticeable shade error." > > Yes, I'm sure plenty of polarizers have shade error. All I'm > saying is that > there shouldn't be any intrinsic reason for them to have more > shade error > than standard shades. > Just to clarify, I'm assuming this means you accept Joel's statement that polarizing-shade sextants have greater shade errors than other types, serious errors (from the standpoint of a lunar). I see no reason to doubt Joel's statement, although we have a pretty small sample thus far. Could the error be related to the mechanics of the mounts, not holding the rotatable glass perpendicular to the optical axis? Alternatively or additionally, the constant flexing of the shade as it's adjusted might lead to more error than simply swinging it in or out of the path? Or how about the polaroid glass itself, could there be problems there?
