A plossl is normally a pair of matching plano-convex doublets with the
two convex surfaces facing each other - close together but not quite
touching.

That would imply that the first lens surface at each end should be flat. Is
that right?

I suspect that this comes into the 'true but not useful' category.

Hmm, well, from what I remember being told, a plossl needn't be plano;
just that the _most_ convex surfaces are facing each other. In reality,
if I remember correctly, that means the crown (convex) halves of
the achromats are facing each other. But I'd be interested to hear if
this is wrong.


Martin
--
M.A.Poyser Tel.: 07967 110890
Manchester, U.K. http://www.fleetie.demon.co.uk