Modification of a Coronado PST

[kev 102 42]

Ihave just orderd a P S T what do i need besides the scope and how do i do the mod thanks....kev

[Peter Drew]

Hello Kev. I used to have two PST's set up as a binocular, however, when the objectives eventually went "rusty" I modded both of them to be used with alternative telescopes. I have a slection of ERF's, the largest being 145mm O/D giving me a number of options regarding apertures. In essence you will need only to include a suitable ERF for your project. Depending on what telescope you intend to use, you may have to shorten the tube to reach focus through the PST rear end, I've avoided this by removing the original scope focuser and making up a new backplate to accept the PST body less its objective as you would an eyepiece, the unit is then focused by using the original PST focuser. It seems that a F10 scope or thereabouts is the best spec for this mod as the original PST was designed for this although I have had excellent results down to F5.6 (Sky 90). I understand from the PST Gurus like Nick Howes, that even better results can be obtained by ditching the PST pentaprism and 5mm blocking filter and instead employ a BF10/diagonal. This obviously incurrs more expense and it might be worthwhile going the easy route for starters, my original PST's were first class and had no noticeable prism or focusing issues. My preference is for binocular viewing, I currently use a Denkmeier model but find that the resulting image is a little duller than I would like. My next project is to build a Ha binocular which should address this issue.

[Merlin66]

Drop me a PM and I'll give you the details!

Basically:

70mm, 80mm, 90mm Baader C-ERF/ D-ERF

Vixen A80Mf OTA

Mod #1

Use the PST black box with an adaptor to the Vixen.

Mod#2

The etalon removed from the PST

BF10 filter

and some adaptors

Ken

[NickH]

As Merlin says...stick to F10 and don't get anything other than the Baader ERF if you want to get really good results at the kind of magnifications you saw at SGL5 Kev