I stumbled across a home built scope with a 4" f15 Jaegers in the front end, which cleaned up surprisingly well. The tube and focuser were a completely different story, not worth saving.
The plan is to make the tube out of 100mm aluminium tube (3mm wall thickness), and fabricate a collar that attaches to the cell for colomation. A spare feather touch focuser will be used at the other end. I am also thinking of segmenting the tube, for easier storage and transportation purposes. A further thought hit me (dangerous with astronomy!), that I could have the tube in two parts (front with the objective, the rear with the focuser), make 2 rears, one normal empty tube for night or white light viewing, one with the internals of a failed PST in there for H alpha viewing (obviously an ERF will be needed as well).
However, while researching baffles, I encountered an issue that I can not find an answer to. This website
http://www.berfield.com/baffles.html seems to have the best description of working out baffle placement, but I can not find a definition for 'desired field size'. I'm planning to use a 2" diagonal for astro or a 2" Herschel wedge for white light viewing, one part of me says that 50mm is right, but another part says no - an eyepiece can not handle 50mm. How do I calculate 'desired field size'?
Any ideas or suggestions are welcomed.
Regards
David