15.02.2021 Brute force Baader 1.25x GPC re-orientation.

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 I am at a loss to understand why PostNord mentioned customs charges for EU internal items on their tracking. Even that there would be delay until I paid the customs charges online. On delivery there was nothing to pay. Exactly as expected.

 The first image shows the rear, AOK Swiss PST etalon adapter and its fixed baffle. I opened the hole in the baffle very slightly to get the GPC to just fit. My lathe was used with a boring bar but it could be easily done with abrasive paper wrapped around a bit of dowel. The difference in diameter of the baffle aperture was quite small.

  The second image shows the 1.25x Baader GPC from the flange side.

  I had no luck with the newly arrived, M48-M42 adapter ring. It was certainly the correct size but did not fit the thread on the Baader 1.25x GPC. The Baader claims a T2 thread but in fact it has a very short M38, male thread. Nothing I have fits this thread and I have quite a collection of things to try.

 Checking the Baader website on GPCs again provided some useful information. The GPC optics are cemented and can be removed and reversed in the flanged housing. The convex side must face the telescope objective. I have yet to try that option in the baffle. Safely trapped at the rear of the etalon in the AOK Swiss, PST housing. 

 Third image shows the doublet, the housing and its locking ring. 

 There was an interference problem with the glass element bulging out of its own housing. Reversal would place the bulge safely inside the nose of the GPC housing. While simultaneously becoming correctly orientated. 

 I have been using this GPC reversed for longer than I can remember. It was a desperate attempt to spread the PST sweet spot. All I was really doing was making the effective field of view smaller. So that the sweet spot seemed larger.

 Fourth image shows the GPC inserted into the slightly enlarged baffle in the etalon adapter.

 Getting the GPC glass out of its housing was a titanic struggle. It was so tight it kept making cracking noises! Yet the advice on the printed label was that the lens could be reversed. The label talks about false colour being produced by incorrect orientation. Whether that would affect H-alpha monochromatic light is another matter.

 The fifth image shows the GPC instructions wrapped around the GPC's nose. The paper label was slightly damaged by trial insertion into the baffle.

 A hair drier was used to warm and expand the housing. Knowing the glass would not expand. I was terrified I was going to damage the glass or take a huge chip out of it! I was using all my finger strength to clamp the glass against my lightly padded, desk top. With tissues as further protection for the glass. After series of loud clicks the glass was finally home! 

My guess is that the housing was CNC machined well undersized. Somebody at the factory didn't bother to use the fit-no fit plug gauge! Inspection/Quality control then failed to pick up the error. Presumably low paid, machine minders in a Chinese sweat shop. It is also possible that the glass blanks were left oversized. There is no credible reason for such an expensive bit of kit should be so badly made. What is the ridiculously tight fit doing to the optical quality?  

€115 Euros [from Baader] is over four times the price of the TS binoviewer GPCs. T-S wants €128! Baader has a reputation for poor manufacturing quality in its products. I have ample proof of this right here. I am tempted to use a fine bladed slitting saw, or jeweler's saw [on the bare housing] to release the pressure on the glass! It can't be doing any good and the locking ring is completely superfluous! It would need a hydraulic press before the glass eventually fell out! Now I am afraid to remove the glass again to do the stress relieving, slitting of the housing.  

 After a rest from my manual exertions I could then fit the very tight locking ring. Then lower the re-oriented GPC back into the AOK baffle. Insertion of the rear end of the PST etalon locks the GPC safely into place. I just have to remember never to remove the etalon without restraining the GPC. Without the etalon housing the GPC nose sits in the baffle by friction alone. Any play, which might cause the GPC body to tip slightly, can be taken up with thin fiber washers. Of which I have lots from a discount boxed assortment. 

The difference in curvature of the doublet element is difficult to judge by eye. Though I can confirm that the convex face is no longer projecting as it was. So it will not come into contact with the rear of the PST etalon. Which was the initial clue that I was using the GPC inverted. 

https://fullerscopes.blogspot.com/2021/07/16072021-etalon-adjustment-continued.html

 

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