I found a cylindrical thing in my photo gear box and I am not sure (anymore) what this is. It seems some kind of converter, as it has a different thread diameter on each side.

What is it, and what's it used for?

The ring lying next to it has a letter P on it, and it can replace the ring on the right hand side of the Mizar tube. enter image description here

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2 Answers 2


Resembles an adapter to mount a camera to a telescope such as a Celestron or a Meed 8". Also, I think it allows an eyepiece to be inserted for eyepiece projection.


Thanks to Alan's first answer I found that this is a Mizar Shinsei adapter "for Astro Photography with 35mm S.L.R. camera". The particular rings I have seem to fit an M42 camera mount.

Below picture shows an excerpt of the Mizar catalogue, with my part highlighted in blue. enter image description here

  • The P on the mount ring stands for Pentax, M42 also having been known as Pentax Screw mount. Jan 13, 2018 at 11:33

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