Yesterday I got a NexStar 114 GT for free from a guy who was just going to take it to the dump. The electronics work, and it was just left outside without the caps on. Basically it is just dirty. I've taken it apart and begun to clean it.

The mirrors are particularly dirty, but I can't see any damage to them. Of course, I don't want to cause any damage to them either. I was thinking about soaking them in water to loosen up the gunk and then first use running water to remove it followed by some sort of cleaner.

Does anyone have some cleaning tips for mirrors?

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"Lisa, in this house we obey the laws of thermodynamics!"

Yes, several books and websites describe processes for cleaning mirrors. I know it has been discussed here before as well.

Be very careful when handling the mirror, a clean towel can support it if you set it in the sink.

Use clean water to rinse off the big chunks.

I buy distilled water in the grocery store.

If it is really dirty, add a drop of dishwashing liquid to the water.

Then, to wipe the dampened mirror, use surgical cotton (not the fake cotton balls, get real surgical cotton). Use gentle circular motion. Do not press down, just let the weight of the cotton do the work. Turn and replace the cotton frequently.

Final rinse with distilled water.

Let it air dry.

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"I'm as accurate as any psychic. And I'm a cartoon!" -- Squidward

"Arrrgh, the laws of physics be a harsh mistress!" -- Bender

I use a very similar routine to auroras:

1) Remove the mirror
2) Use a very gentle stream from the tap to rinse off the mirror
3) Thoroughly clean sink
4) Fill sink with distilled water and a drop of dishwashing soap, enough to submerge the mirror
5) Place folded towel in sink
6) Place mirror on towel
7) Let mirror soak for a half hour or so
8) Using real cotton balls (I throw 'em in with the mirror when I'm ready to start cleaning so they can soak), gently drag a cotton ball across the mirror. The weight of the wet cotton ball should be enough pressure, you only need to drag it across. Use one cotton ball per pass across the mirror.
9) Rinse with disilled water. You can use the corner of a tissue paper to soak up any remaining droplets (there shouldn't be very many), though by holding the mirror at an angle, you should be able to get most of the water off of it.

I could only add doing a final rinse with isopropyl alcohol, but some experiences with it lead me not to recommend it, unless you can get some good stuff from a laboratory. The 70% IPA in the drug store plastic bottles seems to have a lot of nonvolatiles, sometimes.

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The Devil offered me power. I told him I preferred aperture.

Normally I'd agree with the water soaking but maybe not in the case of a super dirty mirror. Since it is old my first idea would be to send it and the secondary out for recoating and let the recoater handle the cleaning. This would be the way I'd go. But if you want to try cleaning it continue reading:

A very dirty mirror like this one seems to be is a good case for Collodion USP. Not cheap but it will get every bit of the dirt in one application. Though if the mirror coating is about deceased it will lift that as well. In such cases the mirror needed recoating anyway so no loss except then you could have let the recoating company do the cleaning and saved the Collodion bill.

Note the stuff makes gasoline seem a fire retardant so use only in a very well ventilated area with no ignition source. This is because the solvent is ether. Nor do you want to fall asleep on the job.

Get only the USP version and I recommend getting it in several 2 ounce tubes (2 or maybe 3 should clean the mirror and secondary). Once opened it is virtually impossible to reseal and will soon evaporate so if you get 12 oz in a bottle expect the remaining part to be gone when you need it again. The unopened tubes should be fine but the one you partially used will be history.

Very dirty mirrors like yours likely will peal off on its own when dry though some may need a bit of tape to get off. With only somewhat dirty mirrors I use a layer of collodion. Then before it is totally dry lay down a layer of cheesecloth and put down another layer of collodion. This way you can lift the stuff off with the cheese cloth. But small very dirty mirrors like yours usually peal off on their own about as well as they do with cheesecloth. You will need a tight dam around the mirror to prevent runoff. The solution is very thin and thus flows through the smallest gap with no help from surface tension to hold it back.

Before the collodion though I'd try soaking then holding under running water with no cotton. Just the running water followed by a distilled (not deionized or reverse osmosis) water. If the coating shows few holes then I'd use the collodion rather than risk scratching it with a ton of dirt that would get in the cotton even with constant changes. If it does have holes and thin spots (some are present in even a newly coated mirror if you look too closely, I'm talking about very obvious ones) then send the mirrors off for recoating instead.

One source if collodion USP is http://www.mavidon.com/catalog/advan...&Submit=SEARCH
scroll to near the bottom of the page for their 2 ounce tubes of Collodion USP. They sell other types as well as remover -- they aren't what you want.

For more info on the process see:
http://www.webari.com/oldscope/atspages/techtips.htm

Rick