I found I need a camera lucida to present my sister and another one to use at summer light at garden.
Neolucida offers them but I dont know when they are available and available ones climbs more than 100 dollars with postage.
I think a 45 degree mirror and a top viewfinder hole is the construction. What else do I need to know ?
ps: I found few papers at web and they always add a beam splitter to the mirror. Edmund scientific sells 17mm beam splitters for 29 dollars ad bigger ones climbs.
I found Bert's link very rewarding.
It uses only a transparent plastic piece or glass , preferably 8x10 inches to 80mm x 40mm and thats all. I found few papers , opened a article and posted there. Everything , angles , sizes , calculations are there. I am attaching the most simple one here again.