Unscrewing the PST Etalon

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pete_w
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Unscrewing the PST Etalon

Post by pete_w » Thu May 26, 2016 7:49 am

Hi,
New here, and hoping to embark on doing a stage 0 mod on my PST (replace black box with an SCT R&P focuser & transfer blocking filters to a 1.25" diagonal). I've been looking for some time for tips on how to unscrew the etalon body from the black box and wondered if anyone here could advise i.e. is there anything I should remove first like the rubber grip ring, are there any "tricks" to removal or is it just a strap wrench and "brute force".
Thanks
Pete

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Merlin66
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Re: Unscrewing the PST Etalon

Post by Merlin66 » Thu May 26, 2016 8:18 am

Pete,
I recommend removing the rubber ring to prevent damage.
Clamp the black box in a padded vise and apply a strong rubber wrench to the etalon.
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

pete_w
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Re: Unscrewing the PST Etalon

Post by pete_w » Thu May 26, 2016 2:37 pm

Thanks for the above info :)

Have also have been looking for the size of the thread between the PST's black box and the etalon, one site quotes it as being M50x1P (not sure what the "P" stands for) so wondering if anyone could confirm that that is indeed the size or, if not, maybe let me know what the specification is for it.
Many Thanks
Pete

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Merlin66
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Re: Unscrewing the PST Etalon

Post by Merlin66 » Thu May 26, 2016 3:59 pm

The threads on the PST etalon assembly are M50 x 1mm pitch
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

pete_w
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Re: Unscrewing the PST Etalon

Post by pete_w » Thu May 26, 2016 5:42 pm

Thanks for the info, much appreciated :)
Successful separated the PST's etalon from the black box. The strap wrench initially wouldn't hold on the etalon body and kept slipping but after wrapping it in a couple of turns of masking tape to improve the straps grip it came off.
Have also successfully removed the eyepiece holder / spacer assembly; I'm now just waiting for all the new bits to arrive.
Thanks for the help will post pictures of the mod when done; acceptable pictures from the mod might take a little longer :)

pete_w
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Re: Unscrewing the PST Etalon

Post by pete_w » Sun Jun 12, 2016 2:33 pm

As promised some pics of the almost complete PST mod, just need some Sun now...
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Re: Unscrewing the PST Etalon

Post by pete_w » Wed Jun 22, 2016 7:01 pm

Got to use the modified PST visually for the first time on Saturday, had some nice views, focusing is so much easier and precise. It seems to give a brighter image, though I'm unsure if this is because the PST black box prism is now gone. I also have a feeling that the image is slightly larger than it was originally.
The sweetspot for this configuration also seems changed, it seems not to cover the whole disc as evenly now, as I tracked across the sun some details would come into sharp view others would fade although there did seem to be compromise positions where all / most detail across the disk was visible to some degree. Possibly I just need some time to get used to the new arrangement...
Anyway hoping to try imaging through this at some point as I now have enough in-travel to get my ZWO cameras to focus.
Thanks
Pete
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