I recently rebuilt a telescope that I made in 1974 when I was just a wee space cadet.
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In 1974 I ground and polished the scope's mirror (6" F/3.8) at Chicago Adler Planetarium's optic shop under the expert instruction of Ken Wolf. Ken gave me a kit and said that I could start grinding the mirror at home. I had such fun grinding that I just kept going and going. In short order I had an F/3.8 mirror meaning that the focal length of the mirror was just 3.8 times its diameter. Little did I know that short focal length mirrors are typically difficult to figure to an accurate parabolic shape and that they are primarly useful in low magnification Rich Field Telescope (RFT) designs.
Fortunately for me, Ken knew what he was doing and figuring the mirror (the final polishing after the mirror has been ground and polished out) only took about an hour. He would say "go around the drum three times like this." and I'd follow his instruction. Then he'd look at the mirror with his Foucault tester and tell me to go around twice with some other stroke. I think it took three iterations to get it right! Recently I completed an 8 inch F/7.5 mirror. The figuring took at least 15 hours and probably twenty iterations! For Ken it would have taken at most an hour. Boy do I have a lot more respect for that guy now!
When I got the parts home I banged together a crude scope. My father bought me a used GEM mount which weighed about 50 lbs for my 6 pound scope. I didn't have a clue as to what vignetting was and I ended up placing the eyepiece way too far from the optical axis.
Despite its problems I had a lot of fun exploring the heavens with this scope and in the summer of 1977 I even stumbled across a faint comet on my own with it (no, I was by no means the first person to see it, but it was very exciting anyway).