[renormalised (Carl)]

My brother just remarked, after telling him about this, was the telescope a refractor or reflector.

Can you imagine trying to build a refractor with a 30m diameter triplet lens!!!!!!

I wouldn't like the job of figuring the lenses....grinding them to right shape, polishing then fitting them together with an oil layer between them!!!!. Then sticking the whole assembly into a carbon fibre OTA. What f ratio would you use....even f5 would make the scope 150m long!!!. Can you imagine f7 or f8, worse still f12 or larger!!!

You'd never use it visually. Can you imagine fitting a 3 or 4 inch focuser on the end of that thing!!!!.

Glad mirrors are the right stuff