Wild T3 question

That's a new one on me and I thought I knew a lot about T3's. Maybe Mike will chime in if he knows what it is. In the mean time I'll look through some T3 books in the morning and see if I can find anything and get back to you then.

I was betting that you would've seen one of these before. For what it's worth, they don't look like an add-on. The paint, screws, wiring and general design are consistent with the rest of the instrument. If it didn't come this way from the factory somebody did real good work.

When I bought this one, there was at least one or maybe two others just like it up for bid.

Wild would do some special things with T3's for people. Mike has a couple of T3's with a rather strange vertical. Instead of 90 at horizontal, they have 45 & 315 at horizontal. If you think it takes some work to get your brain wrapped around regular half verticals, try it with these arrangements.

And BTW - what is your serial number?

And 2nd BTW, is your micrometer a 1 minute or 2 minute micrometer?

When I was a student at the University of Florida, there were a couple of T3's that had that strange vertical reading with 45° being level with the horizon. I never could figure out the reason why. The serial number of the one I was working with was #74437. I heard that they were on loan to the University from the Defense Mapping Agency (DMA).

Wild T3 manual PDF

Unfortunately, this manual http://www.liberatedmanuals.com/TM-5-6675-231-15.pdf does not include the part you show. Hopefully it will be of use. Always wanted a T3 of my own. At one time I had five on my inventory.

The best Mike and I could figure was that by adding the two half verticals (face left / face right) you would end up with a zenith angle. I have seen the purchase order where they were ordered by the Army.

Normally you read the two half angles and subtract them and you end up with a vertical angle.

The reason they went with half angles was because they couldn't put a big enough circle on the vertical to get the accuracy they wanted. So they cut the graduations in half on a smaller circle to achieve the 0.2" reading.

Serial Number is 91609 dated 1969

The micrometer reads 0-60. I was stumped as to how to read it until I ran across an explanation on the net of the two styles of micrometers on the T3 and how to read them.

So you have a one minute micrometer. The simple way is to just double the reading. But the way the NGS guys used to do it is they would read it once, turn the micrometer off center and then recenter and read it again - then add the 2 readings. Hopefully the two readings would be the same, but they felt they got better overall results by reading it twice.

The T3 at the Smithsonian is serial number 91599, seven lower than mine with the same contract number (DSA-700-69-C-G570) and FSN (6675-411-5446) and it does not have the tubes.

That's strange and interesting. Nothing like that on the T-3 here (SN 91025). Not even screw holes for the brackets.

Have you tried sending the pictures and questions to Jürg Dedual, who runs the Virtual Archive of Wild-Heerbrugg? His e-mail is

j.dedual@gmail.com.

Good luck, and let us know!

Cheers,
Henry

I have looked through several brochures, manuals, books & price lists and can find nothing like this described, so I'm at a loss.

I'll send this link to Juerg, Mike & Nathan and maybe they will have some ideas.

Nathan just emailed the following:

I'll check into it it... Jürg may also have a idea- those modifications are ones that I've not seen before on any theodolite. The insulating ring seems pretty unusual in addition to the sighting tubes... very unusual.

Nathan

Some of those were auctioned off on the government surplus website last year. I made a few bids but they went higher than I was willing to go. So, I have not actually seen one in person. My thinking on those auxiliary scopes is that they are just for use at night to make finding a particular star easier. I think if you connect a lighting kit to your T-3 when outside at night you will see that you can use them to align with the star of your interest.
BTW... I don't suppose it's for sale?

I emailed Jürg late last night with the photos, serial number, and the other numbers on the instrument. I'll post any information he provides.

My T3 has nothing like that, but I am pretty sure that is to help aim at stars. In my old age I find it more difficult to aim the scope at a particular star, and have to fumble around with a flashlight lighting up the standard "roof centering pin" on the reticle illumination knob on top.

This is one of the instruments from that auction. There was one other instrument with the tubes in that auction. That instrument had an additional modification to the horizontal fine motion that I didn't notice until I'd already been outbid.

The horizontal fine motion has been rotated 90° clockwise, a second knob added, an arm added to the base of the U-standard and some sort of scale.

Edit: I just noticed that even though this one has the tubes like mine, it does not appear to have the insulator and the brass ring to supply power to the tube lights.

I believe that I will hold on to this one for now but I have two other standard T3's that I might be convinced to part with.

Jürg Dedual will represent the final authority for this, but I believe the earlier posts regarding use of this modified T-3 have some merit, but also serve an additional purpose from the original suggestion as an auxiliary night-time sighting pointer- the following explanation may suffice until we can get a definitive answer. I don't have one of these in my collection to confirm my suspicions- perhaps Mr. Ward can use my explanation to confirm.

First, the thought of each tube being an aide for night-time sighting seems logical- each tube is mounted at the same height of the black arrow pointer on each side of the telescope- and having a lighted crosshair at night would aide in pointing towards a star/or similar object. An additional explanation for these tubes also exists...

Jürg has a similar T-3 (a T-3R) in his collection which was set up for a small camera (German name of the camera was "ROBOT") which was installed opposite of the vertical circle and set up to record the image of the vertical elevation reading. (Pictured below; the modification for the camera setup is is not present on the example that Stephen Ward showed- possibly not installed per contract; or installed but later removed?)

The Dutch website of Mr. Nicolas DeHilster also describes a similar instrument , quoting: "Soon after other institutes and companies in the Netherlands started using T3s as well, but so far I have traced only seven of them; at least two were used at the University of Delft (serial no's 26595 and 33172) and still remain in their collection. The 26595 is a T3R (Recording) on which it was possible to mount a camera on the tube to photograph the circles, allowing interpretation afterwards using a microscope."

http://www.dehilster.info/instrumenten/theodolite3/index.htm l">Nicolas DeHilster's website on T-3

Dutch Recording T-3R

The following 2 images are from Jürg Dedual's inventory of instruments, I want to credit him for their use here.

And the "ROBOT" camera intended to be used with this and many other scientic instruments (timers, aircraft instruments, microscopes, etc)...

On these instruments, it appears the additional light tube on top of the telescope is necessary to provide lighting to the micrometer at all times; (otherwise when the operator switches the micrometer from vertical to horizontal reading the vertical reading is dark) - this would be needed if recording elevations at night.

The tube is open on one end facing the observer -but the other end of the tube is blocked by the snap-in light source; so this doesn't seem to be a useful accessory for actual sighting-in at night; instead I think that the faint crosshair /etched recticle was installed to confirm or actually view that the vertical elevation was lighted and make sure it was visible for the ROBOT camera to acquire the image. (some exploration of this thought at night with the T-3 would confirm, but I don't have an example like this to inspect.) I could also see the length of this extra tube not being long enough to be viewed at the eyepiece also being more of a function of balancing the weight equally on the telescope- Wild made every effort to keep any inbalance to the telescope at a minimum.

The presence of the lighting bulb in the extra tube necessitated a method of powering it from the electrical contacts built into the T-3; apparently it was deemed useful to provide an insulated mount to the telescope by insertion of the phenolic-resin disk on the inside of the vertical circle with the electrical contact bridging it to the vertical circle housing.

Later versions of the T-3 with built-in autocollimation (the Wild T-3A) used a external wire running alongside the alidade standard to the side-mounted light switch and then up along the telescope to power the collimation eyepiece... with a slip ring along the edge of the vertical circle to transfer power- which was not as nice as having all power circuits mechanically integrated internal to the theodolite- but perhaps was deemed sufficient.

a design note- Wild apparently tried very hard to minimize any external wiring on their instruments, perhaps due to the expected failure-points that exposed wiring provided over time with wear and tear- having their lighting circuits built-in to the internal mechanisms with electrical contacts/ slip-rings increased complexity and cost... but this is a common feature of their Swiss design.

*I note that Mr. Ward's instrument has had the index micrometer assembly removed/ worked on at some point in the past, - (possibly to replace the ROBOT camera attachment) - in the first picture posted by Mr. Ward, the dark spot/ hole on the right-side of the upper alidade-yoke housing indicates that the set screw has been accessed, and the wax-sealant was not replaced- this would not have been that way from the factory (the similar hole on the left yoke (where the vertical circle is) is still filled in with the green paraffin wax)

That is my short explanation thus far... any corrections, additions are welcome!

-Nathan Drummond

Mine does not have the additional light on top of the standard near the micrometer knob like the photos you posted. Mine also does not have the relocated/redesigned horizontal fine adjusting setup like the one you posted.

I took a real close look at the tubes. I can see a paper-thin gap between the bottom of the tubes and the telescope so I know that they're not optically connected to anything else on the instrument. I don't have bulbs for the lights on mine, but I removed one of the lights and used a small LED flashlight to illuminate the back end of the tube. When I do that, the view from the front of the tube is a bright white cross-hair on a black background. Having seen the cross-hair back-lit like that I'm pretty sure that the tubes were used as a sighting aid.

It's odd that none of the these variations show up in the manuals.

Good eye on the set screw. Looks like it was accessed at some point and they used a different shade of green wax to re-seal it. The screw is actually covered with a light green wax but they didn't fill the hole flush with the surface.

Thanks for all of the information. I was familiar with Nicolas Dehilster's T-3 website and Jürg's site but I was never able to find any T-3 variants other than the autocollimation versions.