I have been reading about “first contact” red polymer for eyepiece, mirror, and objective cleaning, which led me to looking up different chemical cleaners for glass. I have used (Individually, and on different occasions) original windex, distilled water, isopropyl alcohol and proper wiping methods with pec pads and lens cloths, and even premium cotton swabs— all pretty successfully for my mild cleaning needs of corrector plates, mirrors, objectives, and eyepieces.
BUT I never had to clean anything wildly difficult from an objective: tree sap, avian excrement, paint, stain, etc.
First, has anyone had to deal with something heinous like that, and how successful were you? What worked? What didn’t?
Second, I luckily do not have this problem, or else I would be sharing pictures right now— but I like to be prepared with what it would take to do should I come across some sad telescope in a bad condition (as I do hunt the Craigslist forums/garage sales).
Thanks for your insight!