Posted by Andrea Tasselli at 07:51 on 2010 Mar 26
Well, actually the explanation might be quite simple: The imager adjust his/her gain level so as not to over-expose any area of the planet. As Saturn closes in toward opposition (at very small phase angles) the rings brighten up considerably but not the globe. Keeping the same gain as not to overexpose the rings yields a lowered signal for the globe and hence more muted colours. By the way during this opposition I haven’t noticed any undue dulliness, since the rings brightness increase is very small (small rings angle).Andrea T.