Cleaning Large Newtonian Mirrors: How to?

[Rodstar]

Just wondering what methods people use when cleaning large newtonian mirrors (let's say 15 inches and bigger)?:shrug:

The method often talked about, where the mirror cell is removed and the mirror is literally washed down in the sink (Iceman has an article about this method in the Projects and Methods section of this site), is obviously not practical and much more risky for a 20 inch mirror.

In their promotional video, Obsession talk about washing the mirror in situ in the mirror box, and using distilled water with just a drop of mild detergent, spraying first with a spray bottle, and then washing the mirror down with distilled water, literally poured down the face of the mirror. The problem with the Kreige method is that it requires removal from the mirror box of all wiring, encoders etc. For someone like me with minimal technical know-how, pulling out the wiring is a frightening idea...:scared:

I found a method on Royce's website, which involves acetate (if the mirror is really dirty), then Windex, then human breath.

John Bambury suggested to me the other day pulling the entire mirror box away from the rocker box to avoid the problem with wet wiring. That is still a little terrifying for me.

What do you use for wiping material? Pure cotton balls? Something else?

I would welcome any comments and experience.:thumbsup:

[wavelandscott]

I've only got a 12.5 inch but I take the mirror box away from the wiring...and follow the "Krieg" method...I use sterile cotton...

You've got to have a lot of dirt to warrant washing a big mirror anyway...in my opinion. I think you've got to have a lot of dirt on it before it will impact the views.

Like many things, it will never be "clean"...the moment that you finish washing it will begin to accumulate dust almost immediately.

At only a few weeks old I'd be surprised if it needed cleaning already :D

[h0ughy]

Rod I am sure you got that DVD from Obsession , watch it again!!

[beren]

Ive been meaning to try these static brushes to see how effective they are http://www.optcorp.com/productList.aspx?uid=105-180-181&pg=0 , maybe one idea without going the full way with liquid cleaning although Im not sure if these are suitable for mirrored surfaces

[mill]

Please do not use those static brushes :(
Distilled water is still the best way to clean a mirror.
Brushes will scratch the mirror if used improperly.
And if the dirt is not dust, those brushes won't get it off anyway.

[Rodstar]

I emailed Peter Read (SDM), and this is the method he recommended for cleaning the mirror without pulling out all of the wiring / azimuth encoder:

"1.Your scope should be assembled

2 Cover the encoder with a piece of plastic or put a garbage bag in the rocker box

3 Now put some towels down in the rocker box and coming out the back end.
(make sure that the lower collimation bolt doesn't foul on the towels when moving the scope - you can remove the grey plastic coll. bolt cover to give you a tiny bit more room)

4. Point the scope up to the Zenith

5. Add 1 drop only of dish washing liquid to 2 litres of distilled water

6. Pour some (perhaps 1/3 fill the mirror) on your mirror and starting in the centre run your cotton balls or makeup removal pads in an ever spiralling motion. Keep changing pads and work your way out to the edge of the mirror - round and round and round.

7. When you are satisfied with the cleaning, tip your scope to the horizon and let the excess water tip out onto the towels

8. Now using distilled water only spray or pour plenty of water over the mirror and let it sheet off while the scope is still in the horizontal position. ( by the way this should be the first step to remove any grit or larger particles) The water should actually drop off the mirror hitting the ground completely missing the rocker box. Hard to believe but true.

9. Let the mirror air dry

10. you will never be able to get it perfectly clean and dust will collect on your newly cleaned mirror.

The simple rule is if you have to ask "Does my mirror need cleaning" then the answer is "No!""

That has certainly answered my questions.....and will make it much easier for me to clean the mirror without having to disassemble everything. Phew!

[Starkler]

I wouldnt waste distilled water for the soapy wash phase :shrug:

[ving]

paul hease washed his 18" recently but i cant remember what method he used... might do well to ask him :)

good luck rod :)