I have been fiddling with my 4" f18 scope, and I thought you might be interested in some images of it.
I picked up a brass achromatic objective, dating from the 19th century (it cost me $5), and I attached it to a pvc tube from an old downpipe. I recently upgraded the 2" focuser on another scope, so I have put that on it, attached some tube rings I acquired from a defunct telescope store, made a vixen-style dovetail and mounted it on my home-made "semi-
The images through the scope are excellent: I ran it at 200x on the Moon and double stars last night, and it gave text-book Airy discs with no image breakdown. It is a bit less bright than a coated lens (no coatings in the 19th century!), but it shows almost zero
It is of course a bit long for taking on a plane but it is a lot of fun. It also requires a bit of lying-on-the-ground-viewing at the zenith unless I make the tripod a lot longer!
Dean