Cleaning a mirror

Hi.

First post here, hopefully one of many. I was recently give a telescope, 8 inch dob, by a relative. It hadn't been used for 3 years and in that time was stored in a pretty damp and dusty environment. I took out the mirror and blew off the very thick layer of dust. This left sort of a greasy film on the mirror which I then cleaned using cotton balls, distilled water etc. Now, even though it's spectacularly different the mirror has a whitish look, particularly around the edges. It seems OK even though I haven't had a chance to test it out given the cloudy skies, probably needs collimation, but I wonder if there is something more wrong with the mirror or would more cleaning help? I'm reasonably pleased with my cleaning, given what it was like, but any suggestions to further improve it would be welcome. Thanks.

Not sure what the "whitish" look would be but I'd recommend you reassemble and test the 'scope before (and if you need to) go at the mirror again.

mossief1965 wrote: Hi.

First post here, hopefully one of many. I was recently give a telescope, 8 inch dob, by a relative. It hadn't been used for 3 years and in that time was stored in a pretty damp and dusty environment. I took out the mirror and blew off the very thick layer of dust. This left sort of a greasy film on the mirror which I then cleaned using cotton balls, distilled water etc. Now, even though it's spectacularly different the mirror has a whitish look, particularly around the edges. It seems OK even though I haven't had a chance to test it out given the cloudy skies, probably needs collimation, but I wonder if there is something more wrong with the mirror or would more cleaning help? I'm reasonably pleased with my cleaning, given what it was like, but any suggestions to further improve it would be welcome. Thanks.

Can you break down your cleaning procedure for me step by step?

I say to test the scope first, and if you cannot good images, then I would strongly recommend re-aluminising it by a professional workshop.

Yours, Aubrey.

The 'whitish marks' may be little more than mineral deposits from the cleaning process.

Whilst it's true that it may be oxidisation it would most likely still be overkill to consider re-aluminisation if the majority of the mirror is unaffected IMHO. Recommending such an expensive (and potentially risky) procedure before getting more information seems like jumping the gun to me.

martinus wrote: Can you break down your cleaning procedure for me step by step?

Additionally does the scope have any special coatings? if you used anything other than distilled water there could have been a reaction with the coating. Or the 'greasy film' may have reacted with a coating, or perhaps you just didn't get all that greasy film off.

Assuming you were careful with the cleaning and there is no damage done to the aluminum then in the worst case you could wash the coating and any remaining 'greasy film' off with acetone and rinse again with distilled water. Thats almost a last resort though as you will loose any coatings from doing it, but worth a try before even thinking about re-aluminising!