That isn't so big, this is bigger, got this one yesterday too:
Edit: it needs repair from a bad scuff but have a specialist already agreeing to grind and polish this 30 pound monster for a longer focal point but the work is not cheap at 1,000 dollars, beats paying the going price for a new 13.5 inch diameter lens, if you can even find one. The outside diameter of the mounting structure is 14.75 inches, not counting the posts! I could just as well find a used telescope mirror and make a laser beam expander with that, but I like refractors. Also, finding a super long focal length in a telescope mirror isn't common either, so I opted to just have this one reworked into the focal length I want.
I'm not looking for perfectly spread IR light, just a lot of it in a collimated beam. I don't know if this can be used at 808nm yet, if not I will use it in the visible light range as a beam expander, possibly even a camera obscura. I bought this because of the possibilities, as soon as I learn how well it will pass 800nm I will make that decision and have it cut and polished accordingly. I'm hoping it has relatively low loss for IR, don't know yet as it is still on the way to me in the mail. This is a plano-convex lens, or flat on the other side and 3.5 inch thick in the middle from back to front..
