Coronado PST modification

[lnlarxg]

I recently saw in a post here in SGL with people’s dual scope rigs, and one of them has a Coronado PST screwed onto the back of a refractor, and a few comments mentioned PST is a match in heaven for that scope

any remembers that or knows which scope it is? Quite interested in looking into that!

Cheers!

[JamesF]

I believe the Tal 100R was a very popular donor for the mod you're talking about, but they're rare these days.  Once my observatory is watertight I have an Evostar 102 that I intend to mod for mine.

James

[Stu]

You should find plenty of advice on the forum about making a PST Mod. It is not as straightforward as sticking a PST in the back of a scope as I’m sure you would understand. You need a full aperture D-ERF at the front, or a sub aperture one mounted internally, plus to get the position of the Etalon right relative to the focal point which normally involves cutting the tube down. Removing the gold tube from the PST can also be a bit of a challenge.

I cheated, and bought one ready made, and very good it is too. @Merlin66 has some great instructions if you send him a pm.

Scope wise, the original PST is a 40mm f10, so you need something like a 100mm f10 (it’s the f10 bit which is important, it needs to be f10 or greater). I have a Vixen 102mm f10 based Mod, but the TAL 100r or RS are ideal and I think the 102mm f11 TS/Lyra/Altair clones also work well.

[Merlin66]

As mentioned, the basics are:

f10 donor telescope

Energy Rejection filter up front

The etalon from the PST placed -200mm inside the prime focus.

A Stage 1 mod uses the PST "Black Box" - with the gold tube removed, a Stage 2 Mod uses only the etalon from the PST (and sometimes the blocking filter).

Drop me an email address for a copy of the PST Mod write-up.