[JA]

Originally Posted by OzEclipse

An interferometer, the Narrabri Stellar interferometer that operated from 1963 to 1974 was constructed of many 15 inch polygon cut mirrors.

Modern professional large telescopes are being made as multi-segment mirrors with the segments driven to provide adaptive optics - optics that adapt to atmospheric changes.

You would be hard pressed to align all the mirror tile segments to the required accuracy. All the tiles would have to have their curved surfaces

Curved - Ok there goes easy DIY

Originally Posted by OzEclipse

sit on the theoreticalperfect curved surface with errors less than than 100 nanometers just to perform like a mediocre mirror.

Joe

And then there's that

Thanks for quantifying that Joe and also to Glen for your response

Best
JA