Brings back memories - I ground a 30 cm reflector back in my teens. Was interesting to read how they no longer use two glass blanks, instead use one blank and one tile grinding tool. Took me most of the summer to get the mirror ready for coating, and that was working on it most every day for at least an hour. All very worth it when everything was finished and assembled and we pointed it up into the night sky. Nothing like a clear cool fall night and a decent (if amateurish) scope to contemplate extremely large numbers.