PST modification plans

[riklaunim]

I have a PST, with the dual-stack addon even, but I want to give that baby more aperture. I'm thinking about making a typical mod with the black box intact, just connected to an OTA like:

- 102 mm Mak

- Vixen VMC 110 or 95

With matching ERF on the front. They have big focus travel so I assume there won't be a problem with setting them up that the PST part will reach focus. Anyone used such scopes for this? Can the extra unit from dual-stack setup can be somehow incorporated into the design?

If that won't work then some smaller and "slow" achro would have to be used - but I would also want to avoid the need for any cutting of the OTA

[Peter Drew]

I made an SCT/PST mod based on a Celestron C5 and using a full aperture ERF. I have to say, that although it worked, the views were disappointing compared to my 5" F10 refractor mod using the same ERF and donor PST.     

[Merlin66]

The double stack SM40 works in a collimated beam. To utilise this filter you would need a completely different optical arrangement (Something like the MARCON design, which ends up pretty large and heavy).

IMHO a 100 or 125mm f10 refractor is the way to go. Getting the necessary -200mm can be problematic with some OTA's.......