Help identifying 'Astro' microscope objective please

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jmc
Posts: 238
Joined: Fri Apr 17, 2020 3:14 am

Help identifying 'Astro' microscope objective please

Post by jmc »

I need a bit of help identifying a mystery objective please. The person I got it from knew nothing about (it was from ebay from a vendor who dealt in general second hand stuff, but wasn't a microscope dealer).

The mount seems to be the same diameter as RMS but is a finer pitched thread. I could get it about 1 turn onto my Olympus BHB and that was all. It has a second set of threads which are larger diameter and coarser.

It is marked as 'Astro 232XVIIIa' but it could be 'Astro 232 X VIII a' based on the spacings of the characters. There is also a faint number '51' in the space between the two sets of threads.

It is relatively low magnification and the diatom picture was taken with it. It needed the Abbe condenser stopping right down to get anything with it, and the contrast needed boosting a lot.

I've measured the transmission spectrum through it, and it goes down to about 320nm, which rules out it being made from purely quartz designed for short wavelength UV work (I always check new lenses for transmission, especially unknowns like this one).

I couldn't find anything similar online, and any advice is welcome on who may have made it and when. I know Astro Berlin made a wide range of camera and cine lenses, and they certainly did 'one offs', but I have been able to find no reference of them making microscope lenses. However the way 'Astro' is written is very similar to the font and style on an Astro Berlin 60mm Gauss Tachar I have seen online, which made me wonder if it was made by them.

Thanks, Jonathan
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DSC_9422 Astro abbe stopped right down mod lab small.jpg
Jonathan Crowther

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