PST Mod on a SCT

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MapleRidge
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PST Mod on a SCT

Post by MapleRidge » Fri Sep 08, 2017 11:16 pm

Hi everyone...

A question for the modders in the group.

What success would I have if a PST etalon mod was fitted to a SCT scope (f10 Meade ACF) using a full aperture ERF? My larger aperture project has been impacted by poor seeing and the need to run f30 with the Daystar Quantum has not allowed a lot of productive time.

My hope would be to allow images to be taken at prime focus, with ah larger FOV and shorter exposures than the Daystar requires when seeing doesn't justify the long focal length set-up. I realize that there will be a 'sweet spot', but if enough to do some wider field images around the active regions or proms it might be a worth while addition.

I'm only asking to avoid buying a PST and finding out it was a wasted effort.

My other option is to move to a smaller OTA with the daystar in an effort that seeing affects it less...but again, need to spend more money :?

If you have any thoughts or experiences I would appreciate hearing from you.

Thanks,
Brian
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Maple Ridge Observatory

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Merlin66
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Re: PST Mod on a SCT

Post by Merlin66 » Sat Sep 09, 2017 12:44 am

Brian,
Yes it can be done.
Having a full aperture ERF is a bonus few of us have.....
The "key" is to position the PST etalon at the majic -200mm inside prime focus.
Note: if you intend to re-use the PST "Black Box"- a Stage 1 Mod, then you may be a little disappointed - the standard 5mm BF will severely limit you.
A better solution would be just to re-use the PST etalon - a Stage 2 mod and invest in a larger BF say BF15.
Also, in my experience not all PST's are the same....some are good, some are bad and some are "Wow - now that's great"
A good PST result gives a good mod result.
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MapleRidge
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Re: PST Mod on a SCT

Post by MapleRidge » Sat Sep 09, 2017 2:38 am

This was what I thought, but the majority of mods are on on refactors so I didn't want to make assumptions. I have a Lunt B1800 blocking filter that can be used with a stage 2. I still have some parts for an earlier start on a stage 3 mod, but dropped it when the Lunt DSII module was set up as a mod. So far, the pressure tuned lunt etalon has not been successful on the 25cm OTA.

Will have to keep an eye out for a PST.

Brian
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Maple Ridge Observatory

Cambray, ON Canada

bart1805
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Re: PST Mod on a SCT

Post by bart1805 » Sat Sep 09, 2017 2:39 pm

Hi Brian, I thought that the problem to use the etalon at minus 20 cm is the lack of backfocus with the Meade or Celestron SCT's.
The Intes Alter Mak's have a backfocus of approximately 25 cm. So with such a scope it should be possible. Can 't you use a focal reducer after the Daystar to get a bigger fov?
Bart.

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Re: PST Mod on a SCT

Post by marktownley » Sun Sep 10, 2017 8:57 pm

Should work in theory. it's what Valery does.
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