I've been looking into making relatively thin, lightweight gradient index optics, and correctors (for Maks as well as others) were one of the earliest astro applications suggested for gradient index techniques (back in the early '70's at least). If successful, thin Mak correctors might go some way towards obviating temperature equilibration problems.
Since I'm new at this, I don't have all the facts (primarily I'm looking at fabrication techniques, and am not that familiar yet with optics particulars).
Are Mak correctors simple one-piece affairs, or are they doublets or triplets to correct for chromatic aberration? Or does the corrector shape eliminate relevant aberration?