NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sextant Scope Parallelism (was Re : SNO-T Sextant)
From: Bruce Stark
Date: 2004 Aug 14, 20:14 EDT
From: Bruce Stark
Date: 2004 Aug 14, 20:14 EDT
Robert,
You wrote:
"Bruce,
That’s where you got me. If the sextant is vertical you are measuring the
correct angle. If the scope is pointing off center by a small amount then
you see the sun a little displaced from the center of the scope. But isn’t
the sun still in the center of the horizon mirror and therefore in the right
place for the measurement. If you insist on keeping the sun in the center
of the scope I don’t think that you can get the sun to the bottom of the
arc, it will wander off center as you get to the bottom. Can you force it
both to the center of the scope and the bottom of the arc at the same time
if the scope is out of Parallelism?"
Although I think I could answer your question, there's a good chance I'd confuse things further, or even be dead wrong. I'd rather leave it to someone who understands optics better than I do.
Will another List member pick this up?
Bruce
You wrote:
"Bruce,
That’s where you got me. If the sextant is vertical you are measuring the
correct angle. If the scope is pointing off center by a small amount then
you see the sun a little displaced from the center of the scope. But isn’t
the sun still in the center of the horizon mirror and therefore in the right
place for the measurement. If you insist on keeping the sun in the center
of the scope I don’t think that you can get the sun to the bottom of the
arc, it will wander off center as you get to the bottom. Can you force it
both to the center of the scope and the bottom of the arc at the same time
if the scope is out of Parallelism?"
Although I think I could answer your question, there's a good chance I'd confuse things further, or even be dead wrong. I'd rather leave it to someone who understands optics better than I do.
Will another List member pick this up?
Bruce