This would simply be an improved version of those that would give you better color correction and better ability to handle higher magnifications with more portability than the 6” ED and triplet APOs available.
But the issue I'm trying to explain is that the spherochromatism in a 6" f/6 ED doublet could be severe enough that its ability to handle higher magnifications wouldn't be better than a 6" f/6 achromat!
It's a complete mystery to me, why people don't understand that color correction in a lens is NOT the only serious aberration a designer has to deal with. And the more you push a design to its limits, the more ugly things pop out of the mud.
I would very much like to see some design proposals from one of Markus' designers, so we can evaluate how viable the idea is in the first place.
Clear skies!
Thomas, Denmark