Mirror question

I recently bought a used 6" f/5 newtonian so I could get the mount but I was considering keeping the scope for some quick looks.

I noticed that the primary and secondary mirrors both had fading around the edges and being that this is my first experience with a soiled or damaged mirror I was wondering what it is and if it should/could be cleaned. I havn't had a chance to try the scope due to clouds so I don't know if it will cause problems at the eyepiece.

Also, this scope is a Celestron SP-C6 and my first C6 newt. Anyone with any experience removing the primary mirror on one of these?

Thanks,
Mike

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Here's the secondary.

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Moisture has gotten under the coatings at the edge of the mirror and oxidized the aluminum from underneath. The mirrors were probably allowed to get real wet with dew aluminum during use. Dew has dissolved carbon dioxide in it. This is a weak acid that will eat into the coatings from the edges and through any small pinholes in the surface of the coating. Mirror coatings usually have a protective overcoat that resists oxidation, but the edge is vulnerable. Eventually the entire mirror will get a haze over it, but this can proceed very slowly and may take years to develop.

Rolando

Well, I thought for certain that the coatings on the mirrors were at fault and since I didn't have too much invested in this scope I decided to take out the primary and secondary mirrors and have a go at cleaning them.

After researching on the net I decided to clean with warm soapy water in the sink and rinse with distilled water afterward.

Turns out the coatings are fine and with a little light rubbing with my fingers and soap whatever was on there came off. After rinsing there were a few small water spots but I left them there and thought that the views would not be affected anyway.

Collimation afterwards was a little frustrating but I think I finally got it pretty close. I'll have to star test it to be certain.

I gained a little experience disassembling and cleaning the mirrors and it was not that complicated or scary as I thought it would be. I also took the opportunity to center mark the mirror. Everything looks new again.

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