> I have a 12.5", f6 newt (long!) that I am considering cutting in half to
> make for easier transport and storage.
I made a successful 12.5 inch newt/cass with interchangeable front ends a few years ago. It kept perfect collimation even after tops are changed. The secret is three alignment pivots consisting of 3/4 inch holes with a thick washer (a little thicker than the tube material) in each. I first drilled the holes 120 degrees apart on the line where the tube was going to be cut, then cut the tube with a sabre saw. The saw cut made each of the holes into two semicircles, and the saw kerf separates the two halves slightly when a 3/4 inch washer is placed in the hole. Brackets (strips of aluminum with three holes) and bolts on the inside hold the tube halves together and keep the washers from falling in and 1 inch washers on the outside keep them from falling out. There are no degrees of freedom except to separate the two parts of the tube--which you want--and misalignment is impossible. I used three more brackets between the alignment points to help maintain tube roundness and strength at the saw cut. I used these bolted brackets because I didn't plan to interchanges the tops very frequently, but draw catches would do the job as well and would make assembly quick.
Aart M. Olsen aart@uiuc.edu 217-333-7467 College of Veterinary Medicine Univ of Illinois at Urbana-Champaign