Circle T 25mm eyepiece's

[rikroe666]

Last week i decided to buy a couple of 25mm circle T eyepiece's to use with my bino's , the second one i bought turned up today but they are different 

Does anyone know why they have two different size's and why?

Oooh and if anyone as one of the two they would like to swap so i can make a pair that would be smashing?

[nightfisher]

That is strange, i might be able to help out but not till next weekend, my 25mm is the longer one, i would have to take a look through your short one and see what i think

[rikroe666]

Thanks Jules  

It's in excellent condition, same size lens diameter as each other (about 20mm) but one is about 6-7mm smaller in hight?

Might be a bit tricky in the bino's

[John]

There are some other orthoscopic types that use a longer body for the same focal length optics, eg: Fujiyama and Astro Hutech. My guess is that the one with the longer black body focuses at a different position from the one with the shorter body, probably with the latter one needing a bit more outward focuser movement to come to sharp focus.

The company that made these made them for sale under a number of different brand names such as Celestron, University Optics, Telescope House, Orion (USA), Edmund Optical, etc, etc. It's possible that one of these brands specified a longer body and the manufacturer sold off those that were surplus to requirements with no branding on them, other than the "Circle T" sticker.

[rikroe666]

Thanks for the info John,

The only other difference is the lens on the shorter version looks to be sunk in a little more than the taller one by 1 or 2mm, i'm sure optically they will be the same though.

[Astro_Baby]

Possibly the short body one was for a microscope and as a result needed more in focus. John is probably right on that score. These EPs are used in microscopes.