Student microscope

[Radazz]

Here’s a pretty little ‘student’ or ‘library’ microscope. The stand is unlabeled, but the glass is B&l.
I’m guessing 1890s, but if anyone can shed more light on this one I would be eager to hear it.


In nice company.

Enjoy,
Jim

(Image links updated 5-25-18)

[MicroBob]

Hi Jim,

very nice microscope! It looks quite tall - is it 160/170mm tube lenght or longer?

Bob

[desertrat]

In the late 1890s B&L was making objectives for both 250mm and 160mm tube lengths. During that time, the objectives were marked for tube length. If yours is a 160mm objective, and if you have a 160mm scope, you can have fun looking at objects with that objective. I have a similar objective, 2/3" and 160mm, and it gives good images when installed in my A/O 4 series scope.

Contrast is a little poorer than a modern objective, but only because previous owners cranked it through a few too many slides, resulting in a lot of tiny pits in the surface of the bottom element. If you get one of these in good condition, it can give views as sharp and clear in the central field as a modern achromat. The optics don't have coatings, but a typical 2/3" or 16mm objective from this era used two cemented doublets. With such a simple construction, not much light is lost due to reflections. 160mm objectives with the same construction are still being made in China and India.

[Radazz]

This one has a 1” (10x) and a 1/6 (43x) The eyepiece is 10x
I checked this by using a calibration slide to measure the field of view using the original eyepiece and objectives then trying a 1940s set of optics. Perfect match, and tells me it is a 160,
No fine focus.

I presume the ‘library’ moniker refers to a gentleman’s library as opposed to a public library.

Cleaned and lubed it works good enough to be enjoyable to use.

[MicroBob]

How long is the tube length of your microscope then?

As far as I know these old optical glasses were sometimes not perfectly resistant against ageing. I have had old (a couple of decades) packages of slides that had surfaces that were not good any more. I remember a value called hydrolysis resistance as a property of glass mixtures.

[desertrat]

How long is the tube length of your microscope then?

As far as I know these old optical glasses were sometimes not perfectly resistant against ageing. I have had old (a couple of decades) packages of slides that had surfaces that were not good any more. I remember a value called hydrolysis resistance as a property of glass mixtures.

I bought a bunch of old Gold Seal slides on the 'bay several years ago. I had a hard time prying them apart, and when they were separated, they were coated with a thin film of white stuff along with some tiny clumps of white stuff. The usual cleaners like Windex did not work trying to clean them, but I discovered accidentally that dilute vinegar or any dilute acid cleaned them up nicely. When held to reflect a light source, they were covered in a very thin uneven layer of some kind of tarnish, like the the "bloom" on old photographic lenses that led to the discovery of anti-reflection coatings. However, the slides transmitted light fine, and I've been using them to make temporary and permanent mounts for myself. I wouldn't use them to make mounts for sale, but I probably won't be doing that anyway.

[Radazz]

How long is the tube length of your microscope then?

Tube is 160mm from eyepiece to the socket that the objectives screw into.
The stand is 11.75” (just under 30 cm) tall with the rack down to the bottom. There is no draw tube.
The objectives do not seem to be delaminated.