NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Observations with pocket sextant in the Baltic CROSS POST
From: hellos
Date: 2006 Jul 4, 10:35 -0500
> I described the story in detail on this list about a year ago.
Sorry, I must have missed that.
> On the other hand, my repeated tests with star distances show arc non-
> uniformity as large as 0.6'=36" (at the same places on the arc where
> Freiberger certificate shows 4"). The fault is apparently in the teeth on
> the arc: they are not cut very uniformly.
Huh, so the companies are measuring the arc--and presumably certifying their own
instruments based on that certification--without acutally measuring the *system*
error which would include the teeth?
> Of course, there is always a possibility that my observation
> skills are so poor that my star-to-star tests are all faulty
> and the certificates by Freiberger and C+P are correct.
> But this seems very unlkikely.
Have you corresponded with them to enquire? I would expect them to at least be
open regarding what/how they measured and what avenues for error that leaves.
> I cannot coat the eyepiece. The filter has to be detacheable.
The tinting film adheres with a water-based adhesive, if you apply it dry, you
can simply remove it again, like putting a bit of cellophane in the eyepiece for
a minute. Or, for that matter, you could use a bit of black and white
photographic film, partly exposed and developed. Or probably scrounge a bit of
theatrical gels from your theater department. Not perfect solutions, but enough
to let you try sun sights you mentioned you weren't able to try yet.
I suppose a dedicated user could instead obtain one dark contact lens, and
correct the *eye* instead of the instrument.<G>
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To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
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From: hellos
Date: 2006 Jul 4, 10:35 -0500
> I described the story in detail on this list about a year ago.
Sorry, I must have missed that.
> On the other hand, my repeated tests with star distances show arc non-
> uniformity as large as 0.6'=36" (at the same places on the arc where
> Freiberger certificate shows 4"). The fault is apparently in the teeth on
> the arc: they are not cut very uniformly.
Huh, so the companies are measuring the arc--and presumably certifying their own
instruments based on that certification--without acutally measuring the *system*
error which would include the teeth?
> Of course, there is always a possibility that my observation
> skills are so poor that my star-to-star tests are all faulty
> and the certificates by Freiberger and C+P are correct.
> But this seems very unlkikely.
Have you corresponded with them to enquire? I would expect them to at least be
open regarding what/how they measured and what avenues for error that leaves.
> I cannot coat the eyepiece. The filter has to be detacheable.
The tinting film adheres with a water-based adhesive, if you apply it dry, you
can simply remove it again, like putting a bit of cellophane in the eyepiece for
a minute. Or, for that matter, you could use a bit of black and white
photographic film, partly exposed and developed. Or probably scrounge a bit of
theatrical gels from your theater department. Not perfect solutions, but enough
to let you try sun sights you mentioned you weren't able to try yet.
I suppose a dedicated user could instead obtain one dark contact lens, and
correct the *eye* instead of the instrument.<G>
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---
