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Jim,

If I understand your question correctly, and we're talking about the split
mirror, not the whole horizon mirror, here's my two cents.

First, do you get an image on both sides when you hold the sextant steady? I
don't think you do. Unfortunately, I'm not in a place where I can test that
conclusion.

My supposition is, even though the split image horizon mirror is only
silvered on half its surface, the clear portion of the glass does have some
reflective properties of its own.
When this is combined with the rotation of the wrist, what I think may
happen is the rays reflected from the index mirror on to the horizon mirror
allow the object to subtend an arc through both halves. If your seeking an
answer based on physics, I haven't got one.

In respect to comments about the mirror settling down, that may be due to
uneven spring clip tension where some are tightly made with a lot of
kickback and one or more less so. But shouldn't that cancel out immediately
since everything behind the mirror is rigid?

Interesting question.

Joel Jacobs


----- Original Message -----
From: "Jim Thompson" 
To: 
Sent: Thursday, April 22, 2004 5:05 PM
Subject: Re: How does the AstraIIIb split mirror work?


> Yes Doug, I aligned the split mirror and took out all the errors when I
> installed it.  I plan to do some star-star checks according to Frank
Reed's
> suggestions when I get the CN exam done next week.  Still curious about
why
> the Body seems to appear across the whole field of view though.  "Smoke
and
> mirrors" -- but the physics eludes me.
>
> Jim Thompson
> jim2@jimthompson.net
> www.jimthompson.net
> Outgoing mail scanned by Norton Antivirus
> -----------------------------------------
>
> > -----Original Message-----
> > From: Navigation Mailing List
> > [mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM]On Behalf Of Royer, Doug
> > Have all
> > the adjustments been made according to the paperwork you get when you
> > purchace a new mirror etc.?That will insure all is aligned properly.Very
> > important.

   

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