UHC -E filter coating coming out

[Amit Kumar]

I have the same problem, I just got UHC -E filter from Optolong China, I observed with it and it was dark for my 6" scope. It got some dust so i wiped its back surface with with a soft cloth very smoothly and some of it's surface coating just wiped out !! I couldn't believe. Doest it happenes with other filters also. please comment I am attaching the pic also. 

[Ben the Ignorant]

It happened with early filters from certain brands (Lumicon, I believe), their coatings could be dissolved in water. But that was supposed to occur with 1990's technology only, shouldn't be the case with today's coatings. I have the "Made in Germany" Astronomik UHC-E, and it looks brand new after three years, its exterior layers are a hard material that resists scratching very well. I cleaned it a few times, and there's not even a hint of micro-scratching under a magnifier.

But maybe there was a greasy spot on the filter, and you spread it with the cloth, making it look like the surface is altered?

[Paul73]

Yes, that ain't right. Hope that Ben is right about the grease spot.

Paul

[N3ptune]

It looks like a really dirty filter filled with a coat of dust / grease, are you sure it's not only a film of dirt that is going away?

[Mak the Night]

It might be worth cleaning it with Baader Optical Wonder cleaning fluid or similar to see what happens. Filters, like anything optical, can be prone to smudging from grease spots that can indeed look like there is something wrong with the coatings, as has been stated above. Just rubbing it with a cloth can exacerbate this and spread any grease on the cloth itself over the surface of the filter.

http://www.baader-planetarium.de/com/pdf/opticalWonder-engl.pdf

This PDF may be useful.

[Moonshane]

could the cloth have been contaminated / greasy?

[Don Pensack]

The filter just looks filthy and needs cleaning.

I see this all the time on people's filters because people are somewhat paranoid about cleaning them.

A simple cleaning and the entire filter will be as transparent as the center spot.