NAS member George Livanos is a telescope builder. Here he is shown  with one of his mirrors.  24 " disc of glass that George polished himself.

"The item in the photo is a disc of glass 19mm thick and 24" in diameter. It was an attempt to make a paraboloidal mirror for a telescope of about 96" focal length. The flat back has since been re worked to a curve of about 11 meters focal length. This is to be made spherical and hopefully to an accurate sphere. Maybe used to check glass (or metal) mirrors (up to 24" in diameter) for flatness.

The telescope could also be used to make a parallel reference beam of light, 24" in diameter of moderate accuracy (or maybe of good accuracy).

"In the 1990's the glass blank was ordered from Pilkingtons.  then one side of the disk was ground and polished to an approximate paraboloid. This year I will attempt to grind the back and polish the disk to a sphere of radius 22 meters".

George Livanos

NAS Committee Member