PST etalon tuning, motor drive. Pt.5: Rebuilding etalon housing for NON-Dummies.

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I CAN ACCEPT NO RESPONSIBILITY IF YOU VOLUNTARILY CHOOSE TO COPY MY SKILLED AND HIGHLY EXPERIENCED EXAMPLE. I HAVE BEEN DISMANTLING "STUFF" FOR WELL OVER 60 YEARS.

Ever onwards:

Here we see the etalon, outer housing minus its O-rings. The vital screw rests in its rightful place of honour at the centre of the O-rings. Note the narrow grooves in the etalon housing where the O-rings would normally sit. The O-rings produce far too much friction for motor belt drive. Different lube didn't seem to help [at all] and might migrate into the optics if too runny. Some lubricants are designed to migrate. So be warned!

Here I show how far the inner etalon arc can move. About 160+ degrees. This is with a suitable bar [drill] fitted in a single drive hole. Remember to return the arc to its original [central] position or you might lose vital etalon tuning range. Which would mean dismantling it all over again.

Here I have shown the offset of the screw hole in the outer shell. [arrowed]  You can see that the offset forces the outer shell to fit only one way around. If you tried it the other way the screw would completely miss the hole. Or the shell would hang uselessly off the side of the etalon housing.


And, now, let's pretend I have re-wrapped the inner shell with Teflon tape so I can reassemble the outer shell. The last post showed the Teflon tape wrapped shell. It only remains to put that vital drive screw back in to hold everything safely together.

Then put the knurled, etalon adjustment band back over the etalon shell for the motor drive belt to run on. Finish off with the rear AOK Swiss, PST etalon adapter.

I am awaiting new and shorter drive belts. Once I have them I can confirm what length you will need for remote, Skywatcher focuser motor, etalon tuning. Only after I had ordered the longer ones did I realise that I wanted a much more compact motor arrangement.

The final image shows the etalon back between the AOK adapters. I was able to be far more generous with the Teflon tape this time. For which I was rewarded with improved stability. While I am waiting for the new belts I may as well try one O-ring instead of two.

Click on any image for an enlargement.

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