NavList:

Alexandre E Eremenko wrote:

>I am afraid I missed the original Frank's message
>about collimation test with a laser beam:
> 
>
That was my mistake. There was no such message. Frank demonstrated the
method at the conference in Mystic, but there was no discussion of it on
the list.

>Actually I do not see what role the laser beam plays here
>(unlike in the other, IC test).
>
>What is the difference between this collimation test and the
>ordinary one recommended on the book:
>"look at some remote object, first over the sighting vanes
>(=Celestaire cylinders) and then through the telescope.
>What is the advantage of the laser beam spot here?
>Why not a remote wire instead.
> 
>

The concept of both methods is the same. The laser level replaces the
sight over the vanes. That's why it has to be the carpenter's type. If
the edge is parallel to the beam and the edge is resting on the frame
(directly or via the cylinders) then the beam is parallel to the plane
of the frame. So must be the telescope (more or less) if you can see the
spot through it.

>Another question: Can you (or anyone) tell me,
>which scope of which sextant,
>except the astronomical scope of SNO)
>has a collimation adjustment?
>
>I have NEVER seen such scope, neither on e-bay nor in
>the antique shops, not in the catalogs of modern
>production.
> 
>
It is a feature of the receptacle for the scope, not the scope itself. I
have it on one of my sextants. Two parallel rings that can pivot
slightly against each other are held together with screws on opposite
sides of the pivot. Change the angle by loosening one and tightening the
other. The telescope is fed through both rings and mounted to one of
them. The other one is attached to the fork. This takes care of
adjusting the angle between frame and scope. In addition, the fork
slides in and out controlled by a screw and held in position by a
setting screw. This allows adjusting the distance of the scope from the
frame. I shall post a picture of it shortly.

Herbert

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