Helocoid

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4odonates
Posts: 41
Joined: Sun Oct 30, 2022 12:43 pm
Location: Fairfax County, Virginia

Helocoid

Post by 4odonates »

1. What if there isn't a combination of (extension) tubes that equals the optical tube length (in my case, 132.3 mm)? Is that when I would need to add a helicoid to the rig?

2. Does a helicoid feature a lock to fix its length? Otherwise, I’m concerned the microscope objective might shift position when using a macro rig with a helicoid.

Thanks for your advice!
Walter

blekenbleu
Posts: 146
Joined: Sat May 10, 2008 5:37 pm
Location: U.S.
Contact:

Re: Helocoid

Post by blekenbleu »

A couple of mm tube length error is insignificant with 4x 0.10 objective.
https://www.photomacrography.net/forum/ ... 45#p258045
Metaphot, Optiphot 1, 66; AO 10, 120, and EPIStar 2571
https://blekenbleu.github.io/microscope

Scarodactyl
Posts: 1617
Joined: Sat Apr 14, 2018 10:26 am

Re: Helocoid

Post by Scarodactyl »

There are non-helicoid adjustable length adapters (they just have long threads) which might suit better for your use.

dickb
Posts: 342
Joined: Mon Jul 05, 2010 1:54 am

Re: Helocoid

Post by dickb »

Normal helicoids for photography don't have locks to fix their length. There are some industrial helicoids that do, from Schneider and Rodenstock iirc. Like scarodactyl said, there are non helicoidal tubes that can be screwed together that allow for very precisely fixed lengths. I have one from RafCamera in 58mm.

But for most use cases a few mm more or less are not a problem.

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