2" Non-rotating focus tube?

I'm part of a team that is building a solar physics insturment. We
have two places in the insturment where we need to be able to adjust
the spacing between lenses, and the adjustment should not rotate the
lenses relative to each other, should have better precision than a
simple rail system, and we would like to take the set of lenses out of
the instrument as a set without changing the spacing.

I have found a couple of solutions of the type we need e.g. Helicoid
barrel. Unfortunately the first set of lenses is 50mm in diamteter.
The second is 30mm in diameter. The diameter is too large to fit in
the barrel solutions I have found.

We would rather not make a custom part on this. Does anyone have some
ideas for an off-the-shelf or minorly modified off-the-shelf solution?

Thanks,
JD

.

Relevant Pages

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    (uk.sci.astronomy)
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