Double stack PST mod

[jacquesfrr]

Hello,

I am new on this forum.

I have done a PST mod on a Megrez 110ED and it works fairly well.

To improve the bandpass of my system, I have thought about inserting a second PST etalon just behind the first one. Has someone tried this mounting with success ?

Thank you in advance
Jacques

[Allcart]

Welcome to the forum Jacques. I'm sure somebody must have tried it by now. I would think you would have to remove the 2 lenses that sit between the etalons in order to have a chance of it working. Tuning could be difficult.

[Merlin66]

Doubling up the PST etalon assembly for 0.4A bandwidth can be done.
I have CNC machined an adaptor which mounts the etalon pair together ( retaining the original front and rear lenses)
This arrangement does work BUT I found the tuning a nightmare and in the end gave up.
Mark Townley has done similar but appears to have had more success (or dedication/ patience) than me - there's a thread somewhere....

[marktownley]

Hi Jacques,

Yes, I am in the process of doing this. It does work but does take some fine tuning. The number of variables in the system increases and at the moment i'm trying to get my head around what affects what etc. I've been having some success with it. Here is a picture I took just yeaterday...


big prom ds100 bw by Mark Townley, on Flickr

It's tuned ever so slightly in the wings, but the lack of spicule layer confirms we're running at
big prom ds100 colour by Mark Townley, on Flickr

Mark

[JohnM]

There was a guy in Hong Kong who had doubled up PST etalons mounted on a scope and was producing fantastic images with that set up.
I recall he also commented on the difficulty of getting those tuned.
I've been trying to remember his name, Seems like I saw him make a few posts here.
He used to post a lot of images on CN, but then got caught up in their ridiculous rule against even allowing images taken with modded scopes.

[marktownley]

There was a guy in Hong Kong who had doubled up PST etalons mounted on a scope and was producing fantastic images with that set up.
I recall he also commented on the difficulty of getting those tuned.
I've been trying to remember his name, Seems like I saw him make a few posts here.
He used to post a lot of images on CN, but then got caught up in their ridiculous rule against even allowing images taken with modded scopes.

It was Wah I think...

[JohnM]

Sounds right, I thought I had saved a link to his site in HK because it was good stuff, but I can't find it.

[sashak13]

Hi Jacques,

Yes, I am in the process of doing this. It does work but does take some fine tuning. The number of variables in the system increases and at the moment i'm trying to get my head around what affects what etc. I've been having some success with it. Here is a picture I took just yeaterday...


big prom ds100 bw by Mark Townley, on Flickr

It's tuned ever so slightly in the wings, but the lack of spicule layer confirms we're running at
big prom ds100 colour by Mark Townley, on Flickr

Mark
Mark,
Your project is very interesting for me,
can you tell more?

[jacquesfrr]

Thank you all,

Mark, it's a very nice image. Good luck with your experiments.

Perhaps the difficulty to to realise the tuning is due to the lenses between etalons. Mark, have you realised your experiments with or without these lenses ? As Allcart said, it would be a good idea to remove these lenses.

[marktownley]

Yes, they're removed. When in place there is a reflection from the back of the objective lens.

[swisswalter]

Hi Jacques

welcome to that wonderful site. Have sun, fun and mod. Good luck on the double stack project