If you don't disassemble them, those projection lenses can make pretty fine microscopes. I've got a couple of lenses out of slide projectors and overhead projectors which I use at least weekly for close examination of various things.
The image is fuzzy around the edges, but in the center it's fine. Quite surprisingly powerful. And great for the kids to use. (Might be able to make a science fair project out of this, no? Build a simple Leeuwenhoek microscope for comparison and let the "audience" look through both.)
After WWII, my Pop used to haunt the numerous surplus stores and buy all sorts of technical goodies, One of them was a huge aerial camera lens, about 10" in diameter, maybe a foot. That thing would melt concrete, I think. Weighed a lot.
I also had an 8" or so reflector from a Brownie camera flash unit, focal length about 10" to a foot. Took either 40-sized flashbulbs or with an adaptor, M2-sized. That thing would make tissue paper burn almost instantly.
I almost had an accident with it the first time I tried it in sunlight, since the target tissue started up so suddenly and flared so quickly I had to drop it and started a secondary fire in the normal scattering of dried leaves in the fall. Stamped it out, but not without some panic arising in my little fifteen year old brain. Mom wanted to know how come my new sneakers got so black so soon after purchase.
Moral 1: Don't use tissue paper or other light kindling for a focal target while 'speriminking.
Moral 2: Don't 'sperimink outdoors around other flammables, expecially in the Fall of the year, and especially with a light breeze going.
Moral 3: Don't wear your new sneakers while conducting these initial 'speriminks.
Terry, 230RN
