I would say that the object glasses made by Alvan Clark are the best doublets ever made- in crown and flint.
I don't know about these new-fangled fluorite doublets but discounting the glass types used, I don't think Alvan Clark et al have ever been surpassed with regard to optical figure.
I think, given the long focal lengths Mssr. Clark was working with, spurious CA would have been present, but at a really minimal level.
He was an optical genius, the Thomas Back of his time.