I bought the PST for disassembly, for upsizing.
But from yesterday, I begin to think whether I can downsize it or not. After downsizing, I hope to make it short enough, to be used without a tripod, and for afocal imaging so that I can do some daily snapshot of the solar disc in H-alpha.
With the existing PST etalon adapters, I can add a very small objective lens on the 1.25" barrel end, and a simple 1.25" red filter can be used as the ERF, and the the eyepiece end will be used with a PST-BF5.
For the objective, I found a 21mm f=200mm lens available, that's close to f/10 which makes it an excellent match with the PST etalon module. With an overall length of 200mm, it will be truely portable, and the low power will allow me to use without a tripod.
For example, if I used a 40mm eyepiece, the magnification will be as low as 5x.
The PST etalon module together with the adapters and the PST-BF5 will take as much as 12cm of optical path, so with the 1.25" thread extension tube, it's about enough to take up the whole 20cm focal length, the "OTA" can therefore be a short paper tube.
Seems reasonable, I shall try out this concept when all the adapters come back.