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Here's a physical explanation for Alex' previous results, where his
readings were too large.


On May 27, 2005, at 9:41 PM, Bill wrote:

> Repeated the experiment today and STDEVs were in the same ballpark,
> but the
> angle off the arc had grown by a full minute.  In essence (working
> backwards), the difference between the line of sight through the
> scope and
> axis of the index mirror was 1 inch more than reality based on todays
> angles.  I then did an IE check with the SUN, and overnight my IC
> went from
> -.5' to +.5'.
>
> Despite using the supplied brush on a regular basis, I could see a
> brass
> build up in frequently used areas with the naked eye, and used a
> loupe to
> examine the arc teeth. They could be cleaner. I used a new
> toothbrush (as
> toothpaste has abrasives) to clean the arc until the brass was gone
> and they
> looked clean under the loupe. Then I lubricated the arc and worm
> gear.  I
> still had a little tactile bump when the drum was rotated through
> 60 minutes
> which I had mentioned to Ken, but it seemed to move locations about
> 15-20
> minutes with each rotation as before.  Then I looked at the worm
> gear with
> the loupe.  There was a little smidge of something animal,
> vegetable, or
> mineral that was lodged in the worm-gear (and must have sneaked in
> there
> between bringing the sextant in last night, putting it in the box, and
> taking it outside today). It was barely visible to the naked eye
> when I knew
> where to look.
>
> I cleaned the worm gear and went back out to my parallax test
> range.  Bingo,
> target numbers were the same as yesterday, and IC was back to -.5'
> from the
> earlier shift to +.5'.
>

   

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