NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: ? ? ? Re: ? ? ? Re: Adjusting perpedi cularity of the Index Mirror
From: Bruce Stark
Date: 2004 Oct 12, 11:51 EDT
From: Bruce Stark
Date: 2004 Oct 12, 11:51 EDT
Alex,
I'm having my first cup of the morning and reading e-mail. I've just completed the experiment you asked me to do. Actually this turns out to be the experiment I ran before writing you the first time, but I did it again, following your instructions one at a time to make sure I got it right.
Without the vanes, just viewing the two parts of the arc, the alignment changes from the bottom of the mirror edge, where it's nearly perfect, to the top, where it's nearly a quarter of an inch out. That's because the plane of the front-reflecting surface is not exactly in line with the axis of the sextant. And it's the reason for the vanes (dominoes, shotgun chokes, whatever).
I put the vanes on, taking care that they were aligned perfectly with the inner edge of the flat surface of the arc, and found that their alignment remained the same from top to bottom of the edge of the mirror.
If your index mirror won't adjust so you get the same result, something is wrong with it. Perhaps a part is loose or broken, or the mirror surface not perfect.
Bruce
I'm having my first cup of the morning and reading e-mail. I've just completed the experiment you asked me to do. Actually this turns out to be the experiment I ran before writing you the first time, but I did it again, following your instructions one at a time to make sure I got it right.
Without the vanes, just viewing the two parts of the arc, the alignment changes from the bottom of the mirror edge, where it's nearly perfect, to the top, where it's nearly a quarter of an inch out. That's because the plane of the front-reflecting surface is not exactly in line with the axis of the sextant. And it's the reason for the vanes (dominoes, shotgun chokes, whatever).
I put the vanes on, taking care that they were aligned perfectly with the inner edge of the flat surface of the arc, and found that their alignment remained the same from top to bottom of the edge of the mirror.
If your index mirror won't adjust so you get the same result, something is wrong with it. Perhaps a part is loose or broken, or the mirror surface not perfect.
Bruce
