Was assembling my FS60CB with the extender-Q module today (thanks Matt!) and in removing the objective, (STIFF!!!) accidentally touched the objective with my pinky finger, leaving that damned silvery-purple oil ring.
Tried cleaning with isopropyl, but not a LOT better - should I step up to acetone carefully? Bintel's UHTC cleaning did not much except spread it around
Maybe I am being to careful/low pressure because of it being a fluorite objective...
Not noticeable at all through the scope, but these things have habits of getting worse, attracting dust etc etc. You need to keep fluorite nice and clean