NavList:

Dear Herbert,
I am afraid I missed the original Frank's message
about collimation test with a laser beam:

> If you can see the light spot through the telescope nicely
> centered in the field of view,
> the telescope is parallel to the sextant
> frame.

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.

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 true on some old (and English) sextants the scope
can be easily moved in the direction perpendicular to the frame
(you can do the same with SOME modern forks but not with
all of them). But this is NOT the collimation adjustment.
Collimation adjustment (as I understand it) is the adjustment
of the ANGLE between the axis of the scope and the frame plane.

SNO inverting scope is the ONLY scope I've ever seen,
where this adjustment is possible.
On all other scopes I know, you have to bend the fork to achieve the
same result.

Alex.


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