First light PST mod : how to fine tune Etalon?

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Mathieu80
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Re: First light PST mod : how to fine tune Etalon?

Post by Mathieu80 »

Rusted wrote: Tue Jun 28, 2022 4:57 pm
Mathieu80 wrote: Tue Jun 28, 2022 3:29 pm
Thank you rusted, actually there is an uneven brightness across my field, in each position of the etalon tuning ring.
I deal with that thanks to flats, but this uneven brightness makes quite hard to find the good tuning
Sorry, I didn't know you were using flats to even out the PST imbalances.

I presume you have heard of the PST etalon "sweet spot?"
This is the negative side of using a small aperture etalon with a larger aperture telescope.
Some of our experts here have discussed etalon sweet spots not long ago.

My own PST etalon varies from day to day.
I have removed the outer, ribbed, rubber band and its metal supporting shell.
So that I can physically tilt the etalon itself with an extended rod.
Which is crewed into the hole where the hidden locking screw usually fits.

I also "clock" or rotate my Lunt Blocking Filter relative to the etalon.
I have stuck red tape as a marker to ensure correct alignment each time I set up to image.
I am often adjusting the etalon's position, tuning and tilt throughout an imaging session.
Always aiming for the most even, darkest and most detailed image right across the frame.

Thanks for your message Rusted. Yes i have heard about it but with mythe telecentric system i don’t have any sweet spot, not like in a collimated system with the lenses of the etalon.
Mathieu


Mathieu80
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Re: First light PST mod : how to fine tune Etalon?

Post by Mathieu80 »

eroel wrote: Tue Jun 28, 2022 5:08 pm Mathieu:
Super results from your PST etalon, that is a very good one, just try to turn the etalon or the BF15 on its axis 1/4th of a turn and then check for the best position. (contrast and even field)
Best wishes and thanks for sharing your work.
Eric.
Hi Eroel, thank you for the tip, i did not try to turn the BF15, i will do next time :-)


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