ATM Re: 10x80 collimation

["Bill Cook" <atmj1@conceptsnet.com>]

Concerning the 10x80 Hitlerglass, Dave Groski wrote:

>Does anyone know of how one goes about aligning the prisms when the
unit is disassembled?

Two things to know BEFORE worrying about prism alignment.

1) Those prisms are strapped down HARD. It is common for a prism to fracture
when pressure is removed! I don't want to be scary about it, but I felt a
warning was in order.

2) Don't mess with the filters. Those suckers are a watchmaker's nightmare
probably designed to insure that no German Opticalmen were going to be sent
to the Russian front.

THE COLLIMATION

Without an optical comparator, you will probably not achieve true
collimation. However, if you are the only one using the instrument,
'conditional alignment' will do just fine.

a) Remove the shim from the prism / be sure there are no others.
b) Completely remove both objectives / marking the orientation of each lens
to its cell and the cell to the housing.
c) Lap the eccentric ring surfaces as needs to insure that when reassembled
they will rotate freely.
d) Set your personal interpupilary distance and lock it down some way.
e) Exchange objectives / This alone will probably give you the swing you
need.
f) The best way to start this test is to have the object ring fat to fat and
thin to thin / That gives the greatest motion.
f) If this does not work, remove one objective and rotate the lens in its
cell 90 degrees
g) MARK AND DOCUMENT!!!!.so you can back track logically.
h) Try this at 90 degree intervals with both objectives if necessary.
i) This measure should do you just fine.

If push comes to shove, try to shim an objective to achieve a lateral
movement. This will move the arc a little without inducing too much coma and
astigmatism.

If all this has been done and you are still out - and I cannot foresee
that - you may have 'wedge' in an eyepiece elements (usually the field
lens), or damage to other mechanical parts.

I have answered this on the LIST feeling it might be of some benefit to a
few others.

Kindest Regards,

William J. Cook, Opticalman Chief, USNR-Ret.
Manager, Precision Instruments & Optics, Captain's Nautical Supplies,
Seattle
Editor / Publisher, Amateur Telescope Making Journal
yata, yata, yata
www.atmjournal.com
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