At least three observatories with seven telescopes in active use will
be surprised to learn [that making a 6.5-m primary mirror is impossible]

That should have been five observatories and ten telescopes. I
forgot some. I won't swear I'm not still forgetting others.

In article ,
Fred J. McCall writes:
You can do things with earthbound scopes that you cannot do with
something you're going to shoot into space.

How does that apply to the current discussion? Launching a 6.5-m
mirror monolithic should in principle be easier than having the same
size mirror deploy to the required precision. The problem is making
it fit into the payload fairing.

I wouldn't be surprised if there are "black" programs with the
same difficulty.

Nope. They use a mirror roughly the size of Hubble's.

The ones we know about used mirrors that size. Anyone who actually
knows the current situation -- I don't -- wouldn't be allowed to say.

Remember, they're looking at something relatively close as such
things go.

6.5-m mirrors would have advantages over smaller ones. (I don't see
what distance has to do with anything.) I've seen hints that some
have been built and deployed, but that may be salemanship. Companies
vying for the JWST contract would have had an incentive to drop such
hints whether true or not.

The point is that a balloon does NOT replace a 'first stage'.

We agree on that.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA