How come no high speed triplets?

From: RichA (none_at_none.com)
Date: 11/23/04 

Date: Mon, 22 Nov 2004 20:11:46 -0500

Imagine if you will a market void has been
filled. Right now, the only fast, large aperture
refractors are Chinese 6" f5 achros, with horrible
colour. Not acceptable (IMO) even for low power
deepsky work.

But what if someone offered a 6" f5 triplet,
that had colour like (eg.) a 6" f10 achro? Would there
not be a market for such a hyper-portable large aperture
refractor, or are the buyers of triplets set in that all
they want are true apos and therefore will put up with the
longer focal ration needed to achieve that?
Could something like an 8" f4-5 triplet be produced that would
have correction like a long-focus achromat of the same size?

For those needing better colour correction from the same instrument,
perhaps a Chromacor or filters would be usable?

I do not know what such an instrument would cost and it might
make it completely unacceptable for traditional apo buyers.
The traditional high quality 8" f5 Newtonian with a Paracorr
might be the only rational scope for this kind of work.

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