Hi Lewis,
https://www.cloudynights.com/topic/6...-lens-cleaner/
As far as I could figure from that thread it was never conclusive what happened. That the corrector was originally coated was evident from the glass under the retaining ring, but whether it was a bad job on Meade's part, or ruined over time by the way it was contaminated over the years, or as a result of the cleaning is unclear. My suspicion is the former, but I wouldn't dismiss the other possibilities either.
Realising this scope is old... there were certainly were issues with MgF AR coatings on computer monitors in the 1980's and 1990's - it was quite common for zealots keen on a scrupulously clean screen to rub the coatings off.
However I'm not prepared to experiment on the corrector of a valuable and rare scope, or my eyepieces, so frankly I'd have to say just don't do it and get rid of this stuff if you have it. Leave the experiments for those prepared to risk a cheap SCT that can be replaced easily.
Also..
I've worn specs since the age of 4 - and I get a new pair every two years - and have had coated lenses for decades. While it is true the modern coatings are tough (the pale green-yellow multicoatings have a top layer of zinc cryolite - harder than glass) and I've always thought they could stand daily gentle cleaning, twice I have had pairs where the coatings failed - the first about 10 years ago, and the last was a pair made last year which didn't last 2 months.
I've also seen academic research into the way coatings fail and its primarily the same mechanism that causes aluminium mirror coatings to degrade - all coatings have microscopic pinholes from the day they're made allowing water molecules to slowly get in between the glass and coating, very slowly the pore grows and a flake falls off. It's only a matter of time, though how you store it is clearly a factor.
Using a desiccant is obvious, whereas leaving a dewy wet scope in a sealed box isn't a great idea... and both good regarding the need to minimise the risk of fungus. I also put my scope in full sun after an observing session as soon as I can to make sure it its really dried out and gets a dose of UV.
) for any maintenence (ONCE so far).
