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Taylor Hobson alignment scope as an autocollimator?

Mr_CNC_guy

Cast Iron
Joined
Jul 29, 2018
Location
New England
I picked up a Taylor Hobson Universal Micro-Alignment Unit
model 112/636-139. It seems in good condition and complete
except for the light.

DSC01533.jpg

DSC01532.jpg

This is the place where the light would go.

DSC01534.jpg

This is the mounting fitting. It appears to mate to
a twist lock fixture.

DSC01536.jpg

DSC01535.jpg

The hole seems neither inch .559" nor metric 14.18mm.
No problem, I can make any diameter.

But there is no mirror in the unit that would reflect
the light into the optical path so any mirror must be
part of the missing fixture. A could make the fixture to
hold a mirror perhaps using a slide cover plate as the mirror.

The size restriction, .559", seems like it would
block some of the optical path. I have looked online
for a picture of what the missing part would look
like but have not found one.

Will this work or am I up against some fundamental
limit?

Pete.
 
I've not used the Taylor Hobson Micro-Alignment Telescope, so I can't really answer your question. However, my years of experience using K+E and Brunson autocollimating alignment telescopes, along with Kern, Wild, and Zeiss autocollimating theodolites, allows me to reply in more generalized terms.

From what I've seen, autocollimating telescopes used for alignment necessarily have to allow 1) an autocollimation light to illuminate a reticle [which can be either a "positive" (aka crosshair) reticle, or a "negative" (aka Gauss) reticle], and 2) allow eyepiece microscope viewing of both the physical and reflected-image reticle, at the same time. The common ways of achieving this is by imposing a beam splitter between the eyepiece and the physical reticle.

This beamsplitter can be in either of two forms, 1) a cube composed of two 45 degree x 45 degree x 90 degree prisms mated diagonal-face-to-diagonal-face, or 2) a very thin glass plate held at 45 degree to the telescope optical axis.

One common version of the thin-plate autocollimation attachment amounts to a tube having one end cut at 45 degree to the tube axis, with a hole drilled through the tube wall at the long side of the angled cut. The thin glass is then mounted on the angled tube end. The tube is then mounted through the side of the telescope, between the physical reticle and the eyepiece, so that the diagonal glass is centered over the physical reticle, with the hole through the side of the tube toward the real reticle.

The autocollimation lamp is placed at (or into) the square-cut end of the tube holding the beamsplitter plate, usually with some form of ground-glass diffuser between the beamsplitter itself and the lamp. When illuminated, the light from the lamp reflects from the beamsplitter surface, through the physical reticle, and into the telescope optical axis, projecting a collimated image of the reticle from the telescope.

That collimated image is the reflected from the autocollimation mirror, back into the telescope, which focuses a real image of the reticle onto the plane of the physical reticle. The relative position of the image reticle and physical reticle is viewed through the eyepiece microscope.

After looking at your photos, my guess is that Taylor Hobson used the tube-and-plate beamsplitter, with the tube extending from the boss on the mounting fitting you show in the last two pictures.

I don't know if a microscope slide cover slip would make a good beamsplitter for this application, but it would probably be worth trying.

John
 
I have some autocollimator parts that include a beam splitter. They are old parts left from K&E autocollimators that were used during the Apollo mission. Even have Apollo name tags on them. I don't know if the parts can be adapted to the Taylor Hobson or not. If you want to pursue this, please contact me off-line ([email protected]) and I will take some photos and do some measurements.
 
The K&E and Brunson alignment telescopes are pretty similar, and as I recall, this Taylor Hobson unit is conceptually similar but smaller. I can say from direct experience that the cover slip approach works nicely for the standard Brunson offering.

I may have put a pic of the mount in a previous post a while back.
 
Here are some pictures of the parts I have available. Unfortunately I already sold the parts that came from the Apollo mission, but these still might be useful. I have high res pictures, but you will need to email me.

The unit includes an eyepiece and a light, and it has a slide to swap the position of the prism between the side and end. The light and eyepiece can be attached in either location, but I am not sure that was the original intention, they do have the same threads.

The condensing lens in the light is chipped. There is also a power supply but the plug on the light does not fit the socket and I have not verified that the bulb is the right voltage, or even that there is a bulb inside the fixture. I think this was an attachment for a K&E Paragon Level, but I do not know which model. It does not fit the 71-2022 alignment telescope that I own.

IMG_0939A.jpg

IMG_0936A.jpg

IMG_0935A.jpg
 
Your first picture is of a lamp-housing attachment; the front portion unscrew to take a T 1 3/4 size incandescent lamp. I don't recall which industry-number lamp was supplied by K+E, but I'm pretty sure that the power supply output either 12 or 24 volt. The power supply power cord was fitted with a twist-lock plug (in accordance with Aircraft Industry Association, or later, Aerospace Industry Association specification. K+E routinely provided an extension cord socket to fit the plug.

That lamp housing fit the auto collimation attachment fitting the ocular lens assembly that was used on the last generation K+E jig transit, transit square, tilting level, and line-of-sight telescope. I seem to recall that it would also fit some, but not all of the autocollimating alignment telescopes.
 
Those parts don't look like they would fit my autocollimators.
Thanks for the pictures. It looks like i will have to figure
something out.

Pete.
 








 
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