PST mod 2 for dummies

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daslolo
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PST mod 2 for dummies

Post by daslolo »

The legend of the PST focuser being god awful is real and I want to see up close, so I'm making the mod.

I took apart the PST. Now what?

I'm writing a blog for dummies like me https://daslolo.blogspot.com/2020/02/ps ... -make.html


PST on its way to modding heaven
Quark + Orion 120mm + beloptik
LX65 8" ACF
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Re: PST mod 2 for dummies

Post by Merlin66 »

Daslolo,
Drop me an email address and I'll send you the PST Mod write-up.
(On your blog you remove the front lens from the PST etalon assembly - this is not the preferred method of removing the etalon assembly. It is usually removed as a complete assembly from the Black box/ Gold tube.)
Ken


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Re: PST mod 2 for dummies

Post by daslolo »

Thanks Ken, I emailed you.

I'll start with replacing the black box, it seems easy. I'm almost there!
Perhaps I need to replace the 1.25" helical focuser by a 2" focuser to avoid vignetting but for now I have this question:
How do I fit the ITF+eyepiece holder assembly? I think I would need a M42x.75 female to M32x.75 female which I can't find on ebay or amazon.
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PST on its way to modding heaven
Quark + Orion 120mm + beloptik
LX65 8" ACF
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Re: PST mod 2 for dummies

Post by daslolo »

Tada!
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The ultra cheap lx65 plastic diagonal did the trick, thanks Marty.

Tomorrow will be testing this arrangement, perhaps the 2x barlow can shorten the tube or I'll have to buy a few extensions.

I'm tempted to try out that crazy sweiller telephoto mod http://sweiller.free.fr/PST/indexPST.html
But the images on his website look very fuzzy, his lens might be cheap crap so perhaps spending a bit more on it will take care of that.
In the meantime I got a bunch of step up and down rings...

Do I get this right?
"Now why do we have to put 200mm of back behind the etalon?
The PST is a telescope with a focal length of 400mm. Focal length means distance behind the lense where the beams converges into a focused image. It's commonly represented as lines intersecting (blue in the diagram). The etalon is 200mm behind the front so there is 200mm more to go.
The Fabry-Perot etalon needs beams that are parallel to do its precise boucy light thing but the front lense converges the rays into a cone. To correct that the etalon is flanked by two plano lenses (yellow in the diagram). The plano concave at the front of the etalon turns convergent beams into parallel beams and the plano convex lens behind the etalon turns the now-filtered parallel beams back into convergent beam."
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PST on its way to modding heaven
Quark + Orion 120mm + beloptik
LX65 8" ACF
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