[By.Jove (Jove)]

One thing to check is that projectors and enlargers - even really old antiques - have an IR blocking filter somewhere between the bulb and the film - usually one side or other of the condenser lens. Otherwise you risk the heat from the lamp melting the film. This usually looks like a rectangular or square piece of clear flat glass 3…5mm thick. You can tell if it’s working using your fingers to sense whether the heat is blocked or not.

What works really well are camera lenses from old SLR cameras circa 1979-1985, around 135…150mm. Even a typical f/4 zoom from that era will do nicely.

To make a lens mount cannibalise a rear lens cap, or perhaps a ring from a set of extension tubes for the same lens mount.

NB if you project through the same lens that took the image, geometric distortion is cancelled - even for a fisheye. It’s an interesting thing to try.

I’d be very very wary of old paper-insulated wiring and Bakelite electrical fittings..