How to clean Newtonian primary mirrors

[Dom1961]

I am an owner of a 8"Dob and I was wondering what do I use to clean the primary mirror, are there any special fluids? Or can I use a normal window cleanser? And for dust can I use a glasses cloth or do I need a special cloth?

[scotttumsh]

Dont touch it! dont use window cleaner or anything of the likes! have you used the scope yet? dont worry about a wee bit of dust. try it out first but do not use chemicals on a mirror. get out with it tonight if clear and enjoy it.

[Dom1961]

Bought it second hand, its 2 years old with a fair bit of dust on it, can I use a glasses cleaner to clean it?

[scotttumsh]

please dont be too keen to clean.i seen your post yesterday saying you were getting a skyliner. last thing you wanna do is scratch that mirror. trust me a bit of dust will not harm your views. take it out and try it out first before thinking of any sort of cleaning. you may find it needs collimating however but thats another issue. have fun with it young man

[Dom1961]

Thanks!!Will do!(If the stupid clouds dont ruin it)

[scotttumsh]

will be good to hear how you get on with it, all the best and clear skies!!

[Steve Ward]

I would strongly advise not to clean it yet , the primary mirror in a telescope has a very thin , very delicate layer of aluminium on the front surface , quite unlike bathroom mirrors.

They are extremely easy to damage if not treated gently and cleaning is generally not required unless the mirror is filthy , a little dust will not affect the views ... 

[abberation]

My 12" dob is about 9 years old and hadn't been cleaned. The mirror was quite grotty, worse than your headlamps get when they have gritted on the motorway! After searching google and youtube at the experiences of others I decided to have a go. Bought BP cotton wool and a gallon of distilled water. Took it apart and got stuck in. To be honest I dont think I noticed any difference. Putting it back together and collimating it from scratch was a bigger challenge.  What I did find was that the cheap laser collimator I was using was out of collimation. Once I had collimated my collimator and adjusted the scope things were definately better. Looking at the primary with all its dust  probably makes you feel you have to clean it, but if I had known that for me it made no difference, I wouldn't have bothered. Keeping it in adjustment for me is far more beneficial, but these are my own opinions and may not be shared by others. (Many folk are for cleaning the mirrors but many are against it).

[Floater]

All the 'best advice' on how to go about cleaning the primary mirror boils down to: DON'T.

They can't ALL be wrong ...!?

[ronin]

Cleaning a mirror is a difficult area.

Many say leave it but if you have worked in optics then a dirty/dusty surface is simply never tolerated, every glass and mirror surface is cleaned before the item is used, and often several times during use.

The strange aspect is to clean a scope mirror the general approach is warm soapy water, which is something you would never do in an optical environment.

Depending on how bad you can get a blower to remove loose dust and material.

A fine soft artists brush is another option although getting the surface to a uniform clear stage is not easy.

After that I suspect that a proper cleaning fluid is required, the Baader fluid appears popular.

Light dust etc will make little difference to what you see.

One possible problem of leaving it is that eventually any crud will adhere more and then you need more force to shift it, and that could be when damage is done. Ever noticed that a dusty surface around the house that is untouched then eventually the dust is difficult to remove?

If you are outside and get something like tree pollen on the mirror then that decomposes and really is a problem - almost jet wash conditions. That information came from the ES stand at Astrof fest when I was enquiring about their dobsonian.

Really the only person that can make the decision is you.

If you decide that cleaning is required then go about it sensibly and carefully.