Bausch and lomb 53-70-34 eyepiece--what is this used for?

[Scarodactyl]

I keep seeing these odd eyepieces on eBay from time to time. Can anyone tell me what it is used for?
https://rover.ebay.com/rover/0/0/0?mpre ... 4268547782

[MichaelG.]

Very curious !!
I have never noticed them before.

My wild guess is that the mono/stereo adjustment can 'cancel out' the eye-tube splay.

MichaelG.

[apochronaut]

These were the standard issue 10X eyepieces used on the 240 articulating arm stereo microscope that was mainly used for aerial reconnaissance on either a Richards or B & L light table. The microscope is fitted into a portable suitcase sized kit that contains all of it's aux. objectives( 6 pairs) , the mirrored articulating arms, those eyepieces, as well as a pair of 15X U.W.F. eyepieces and other odds and ends. It could be used as a high resolution version of a mirror stereoscope and additionally at really high magnifications , a portable comparison microscope, or as a standard stereozoom microscope, albeit with higher resolution optics than the lab version, stereozoom 4. The body is considerably heavier than a SZ 4.
The mono mode on those eyepieces, reduces the perspective and allows for a better double monocular image when used for comparison microscopy. That's my assessment but I have never encountered a manual. They may have had an application when used for aerial photography too; possibly with photo sets where the registration was poor.

the system's magnification is range is 2X to 240X .

[Scarodactyl]

Cool! I have a zoom 240 set sitting under my work bench, though it ended up being about 10% mold by weight. It sidn't have any of these though (it did have 3 pairs of uwf eyepieces which were somehow not ruined though, so I wasn't too upset).
(If anyone wants a moldy zoom 250 in a moldy box, minus the uwf eyepieces, drop me a pm and it is yours for free).
I wonder if these could be helpful for people who have trouble with some binocular scopes.

[apochronaut]

They might be , if rotated into the correct orientation. One thing I have not had the chance to do is determine if the 240 pod is an apochromat microscope? There was a bit of a no holds barred attitude to it's production. uncle Sam was pretty much paying the tab because it was all accounted for under the heading of keeping an eye on the Ruskies..... $2,000.00 pairs of U.W.F eyepieces, ultra coating on the aux. objectives. These flip over eyepieces. The whole system was built like a tank.
If they turn out to be, then that might make a 240, one of the hot bargains in stereo microscopes. If they are at all usable at 240X, then they must be really usable at 80X with those U.W.F. eyepieces. To get up there with contrast and resolution, there must be some fancy optics in there, especially circa 1980. They fit right into a standard B & L stand.

I think I will have to pull one apart and see where the extra weight is between it and the stereozoom 4.

[Scarodactyl]

If you need a bad one to pull apart just drop me a line.
edit: by the way, how do you get it up to 240x? Or is that only with the rhomboid arms? Mine came with a .5x auxiliary but that was it, and the baseline zoom range only goes up to 3x.
edit 2: how does the zoom 500 fit into this?

[apochronaut]

Yes. There are 5 pairs of aux. objectives at the end of the rhomboid arms. .5X, 1X, 2X, 2.65X and the 4X. Under the 4X max. zoom, the 4X aux. objectives would provide a 16X objective X 10X eyepieces = 160x. With the 15X eyepieces, you get 240X.
The optics must be apo because in order to get an N.A. to carry those magnifications , they would have to be.
I don't know much about the 500 except that it is a bigger brother to the above but not based on a stereozoom. It is a dedicated instrument. Not sure if it is 500 X or not but that might follow. Might be necessary for certain comparison situations.