Hilger & Watts TA51-2 autocollimator

Dear Peter,

the best manual I have found so far is the one that Dennis uploaded here:

This does explain how to swap the eyepiece from the end to the top and vice versa. But it does not have any details about adjustment. Instead, it says (top of page 9): "All adjustments other than those previously mentioned, are initially pre-set and scaled by the makers and it is advisable not to alter them in any way." So there is no adjustment/calibration procedure given there.

Cheers,
Bruce

A few days ago a HW sled and lambda/10 front surface mirror arrived (thanks Greg!). The sled had originally been factory fitted with a 2" diameter 3/8" (9.5mm) thick front surface mirror, but that had been broken at some point in the past, so the sled had no mirror . The lambda/10 mirror from Edmund Optics is the correct diameter but 1/2" =12.7mm thick.

My original plan had been to bore the mounting hole 1/8" (3.2mm) deeper. But after looking at the mount, I decided that this would weaken it too much. There is currently about 6mm of meat by the finger grips, and I don't like the idea of reducing that to < 2.8mm.

So instead I made an extender ring of of random tool steel. Here are the parts:


At the bottom right is the original mirror retainer. It contacts the mirror at three points opposite the springs and contacts the cast iron face near those same three points, and is relieved elsewhere. My spacer ring at bottom left is 3.3mm thick and agrees within about 1 micron at those three points near the holes. Then I have ground about 30 microns (0.0012") of relief on both sides away from the three contact points.

Here is a closeup of my spacer, with the stock retaining ring underneath it. The grinding is functional not pretty, I discovered that the coolant in my grinder had gone bad and spent most of my time replacing that, so didn't spend the time to make it look nice.



(By the way, if someone here can send me a few BA6 oval headed screws at least 1/2" long, I would be very grateful!)

Here is the mirror sled assembled



The tests went well. The images are much clearer than with my provisional mirror, that I think was not flat.
I've been experimenting with the use of an inexpensive USB microscope to observe the crosshairs.


This works very well:



I can repeat the 0.1 arcsec level without eyestrain!

Cheers,
Bruce

Excellent!