Another PST-Etalon-Double-Stacking-Mod

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Jonas242
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Another PST-Etalon-Double-Stacking-Mod

Post by Jonas242 »

Hi there,

tried to double-stack two PST Etalons with a custom made adapter, works nearly perfect after i eliminated several problems:
- first i had to remove the inner lenses of both etalons (the outer lenses were not removed)
- then i had lots of ghost-images / reflections, expanding the distance between the two etalons moved the ghost images out of the FOV, solved
- next problem was banding, its not so easy to tune the two etalons to each other - i did not really solve this problem, but with artificial flats generated in pixinsight i managed to flatten the image

the adapter to connect the two etalons is simply a M50x1 outer with a m50x1 inner tube with a stop-ring, so it's basicly a m50 extension tube with variable length

here are some pics

PST with two etalons (one with rubber-band, other without rubber band) and the adapter between them:
Image
Image

and here the final test, today ad 5pm, 10% out of 2000 frames, processed in PI, ZWO ASI 178mm on this PST-Mod,
Image

i'm not sure, how to judge the resulting bandwith - is it comparable to a real DSL with front-etalon? more tuning of the etalons needed?

Jonas


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Re: Another PST-Etalon-Double-Stacking-Mod

Post by pupak »

Nice work and excellent result. It would still need a larger objective diameter and you will have an excellent solar telescope.


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Re: Another PST-Etalon-Double-Stacking-Mod

Post by marktownley »

Good result and mod! Welcome to the forum!


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Re: Another PST-Etalon-Double-Stacking-Mod

Post by Jonas242 »

Finally adopted the Dual-PST-Etalon-Stack to my Skylux 70/700 Refractor, it works :)

Image

from left to right:
- Skylux (LidlScope) 70/700 Refractor
- reducer to 2"
- 2" Baader Red-Filter (not visible, inside)
- 2" beloptik UV/IR-Cut KG3 Filter (not visible, inside)
- 2" to M50 PST adapter
- Etalon 1 (inner Lens removed)
- M50 to M50 adapter
- M46 Hoya IPC Polarizing filter (not visible, inside, tilted)
- Etalon 2 (inner Lens removed)
- M50 to T2 Adapter
- T2 helical focuser
- some T2 extensions to reach focus
- Coronado BF10 without ITF (not needed)

Image

look ok i think

Jonas


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Re: Another PST-Etalon-Double-Stacking-Mod

Post by marktownley »

Nice result!


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Re: Another PST-Etalon-Double-Stacking-Mod

Post by christian viladrich »

Nice setup Jonas !

If you go to normal display (i.e. BW and non inverted), then you will have a better look at the current limitation of the images, and possibly find some way of improvement.

If you take the FD image, there is a clear reduction in resolution at the bottom of the image.I can't see no clear explanation to this. Maybe something is not square somewhere ? Nor sure whether seeing condition could explain that ?
This is a bit the same for the last image, with increased resolution to the center of the image.
Maybe you can try to rotate the etalons to see if there is any change ?


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