Second-hand scope: is silver coating a concern?

[blusky]

Looking at a 6-year old catadioptric scope, so I understand a sealed design. Nevertheless, how would the silver coating deteriorate over these years? If re-coating is recommended, how can this be done for a catadioptric? Thanks...

[blusky]

No replies - I guess no then :-)

[glowjet]

As you point out Catadioptric scopes are of a sealed design, therefore the elements do not directly affect the mirror surface as in Dobs or newts, how long does the coating last ? a bit like how long is a piece of string ? with modern techniques and final protective coatings, quite a good number of years, if the scope is stored correctly. Deterioration of the image will be a good indicator of when the mirror needs attention, all that will need then is the scope to be stripped and the mirror sent to a specialist like Williams Optics who undertake such re coating work HTH

[ronin]

Almost unanswerable.

If the scope has been unused and in a shed then there could well be problems.

If used at regular intervals and kept inside then I would say it should be OK.

One person had to take one apart to get the spider that had taken up residence out of it. They left the eyepiece holder with nothing in and a spider found a new home.

I think that most CAT's are silvered then coated, so being sealed they have a long life when taken reasonable care of.

[NGC 1502]

The mirror coating on most Cats lasts many years. A clubmate of mine recently sold a 1970s Celestron SCT, and the original coatings were fine.

If the coating looks ok, then it is ok.

Regards, Ed.