Cleaning your mirror

[NotSoSuperNova]

Hi guys,

I'm looking at getting my telescope prepared for use now that the nights are drawing in and noticed that my primary is in a bit of a mess after a few years of living in my shed. Are there any guides that one might use to bring it back up to standard? I'm fine removing the thing as out of curiosity, one of the first things I did with it was strip it down and reassemble it. I'm more interested in maintaining 'good practice' while handling it and the products to use (like DI vs RO water). Thanks in advance. 

[brantuk]

Try this one :

 

 

[estwing]

I've had my mirror re-coated more times than I've washed it!!!

[Ben the Ignorant]

I've used isopropyl, dish soap, pharmacy alcohol, some so-called specialized photo lens cleaner, and my friends' Baader magical jedi-force superfluid over the years, and found that the product doesn't matter as long as it's mild, and you leave no residue. Pure alcohol and/or distilled water evaporate completely, so...

[Paz]

I know it can be done but the thought of touching a mirror with anything, even for the purpose of cleaning it makes me feel a bit queazy!

I've cleared the dust off my mirror with a manual hand blower and that cleared the vast majority of what was on it and left it looking really good without having to touch anything. You might benefit from trying that first and see what effect it has before considering giving it a wash. Good luck!

[N3ptune]

I tried Brantuk's technique has the video on my 203mm commercial coated mirror, great technique simple and it's has not induce any damages on my mirrors. I did it following the steps and had no problems.

[Dave In Vermont]

You might wish to read this. It's by Doc Clay Sherrod of the Arkansas Sky Observatory (ASO) in the USA. Doc Clay is a widely respected amateur-astronomer over here and an authority on SCT's and other scopes with mirrors. This is his take on cleaning them - and warnings:

http://arksky.org/asoclean.htm

I've used his recipe and it works better than anything else I've used. Brought a Maksutov back to 'showroom-new' after an unfortunate encounter...

Always use caution in cleaning,

Dave

[Merlin]

Check out this no-fuss way. I performed it myself with a 200mm mirror:

 .

[N3ptune]

@Merlin

I liked that video, it's a representation of something realistic with less steps and that works (At least with a mirror with commercial protective coating) He cut's on the paranoia factor it's great to hear that. Also, I tried the exercise of cleaning my mirror with my bare hand and it worked fine for me.

- Although, my well water is really hard and I would never let it dry on my mirrors, a final rinse with distilled water is mandatory for me, it's 2$ CAD for 4l, almost free.

- And I would pick a pure light soap, basic soap ingredient only that is easy to rinse with no fragrance, no concentrated formula, no special ingredients like OXY clean, or even the foam type. The Dawn Foam could be a concentrated formula like what they advertise for a similar product on Dawn's website. 

Pump up the clean with Dawn® Platinum foaming dish soap! Featuring a breakthrough technology that turns liquid formula into powerful foam,

[NotSoSuperNova]

Thanks for the help people. Now, which method to try first.....

[dyfiastro]

On 27/10/2016 at 16:00, brantuk said:

Try this one :

 

 

I recently cleaned my primary using pretty much this exact method.
The only difference was that I used 0 TDS RODI water.

 

 

[kirkster501]

People obsess about this far too much.  Just bung it in the sink as the videos state, let it soak for five mins then a couple of drops of washing up liquid.  Only using your finger tips lightly move them over the surface.  Rinse copiously.  Repeat.  Then, what I do is use some RO (reverse osmosis) water for the final rinse.  You can get RO water from an aquatic center - many garden centers have one.  Maidenhead Aquatics have stores all over the place (I keep fish as well so this is easy for me).  Costs a quid for a gallon of it.  Finally rinse the mirror in the RO water.

Jobs' a good 'un...  Never scratched a mirror yet.  Done this on Newt's, SCT's and RC's.  Never had a problem.

I wish it was as easy to clean a refractor lens. I've never had to do it yet on my FSQ or my TEC.....

[iapa]

On 27/10/2016 at 17:20, Ben the Ignorant said:

I've used isopropyl, dish soap, pharmacy alcohol, some so-called specialized photo lens cleaner, and my friends' Baader magical jedi-force superfluid over the years, and found that the product doesn't matter as long as it's mild, and you leave no residue. Pure alcohol and/or distilled water evaporate completely, so...

Start building your own still?

[N3ptune]

@digitalcyanide

Great work (: thanks for sharing the picture of your mirror. My own mirror looked just like yours when I decided to clean it using the same technique.

https://www.youtube.com/watch?v=8TObET2F-EA

This is a picture of mine, unfortunately at the wrong angle, but it's a clean 8 inches.

@NotSoSuperNova

When I removed the holding assembly with the primary, I noticed SW used loctite on the bracket bolts, I had to clean that mess and go to the hardware store to get some loctite during the cleaning process, to do the same thing has the original.

At this point, why not pass the compressed air inside the tube to remove all dirt? While the back is removed.  (That step was effective also)

[alan potts]

I tend to stick to the rule if you can see yourself in it it's not dirty. Don't really fancy cleaning an 18 inch mirror, for one my sink is not big enough.

Alan

[kirkster501]

14 hours ago, alan potts said:

I tend to stick to the rule if you can see yourself in it it's not dirty. Don't really fancy cleaning an 18 inch mirror, for one my sink is not big enough.

Alan

That's what hosepipes are for......  

[N3ptune]

@alan potts

Hello Alan, I saw notable improvements in my views of faint objects after I washed my mirrors (like day and night) The telescope can gather more light with no film of dust on it's mirrors, they are much more effective.  To me the difference was important..

This is my observation.

[alan potts]

20 hours ago, kirkster501 said:

That's what hosepipes are for......  

As much as I have 3 hose pipes we have not really had much in the way of water for 3 months, though rain is expected today.

Pleased that the OP cleaned his mirror and is happy, I was only trying to say in a joking way that sometimes people do over clean mirrors. I can actully put my hand in the light path on mine and not see a difference but sometimes when they have collected too much dust and muck it is time for a bath. Recently got a new all singing all dancing washing machine but I don't see a mirror cycle.

Alan

[niallk]

On 07/11/2016 at 11:40, N3ptune said:

@alan potts

Hello Alan, I saw notable improvements in my views of faint objects after I washed my mirrors (like day and night) The telescope can gather more light with no film of dust on it's mirrors, they are much more effective.  To me the difference was important..

This is my observation.

Good to hear - I'm hoping that I'll pick up some contrast after a clean:

[sophiecentaur]

I cannot understand how the attitude to dusty mirrors is so laissez faire, bearing in mind that photographers with lenses keep them spotless. Dirt on a lens causes flare and poor contrast but, somehow, on a mirror (which performs the same operation on the light going through) it is not reckoned to be important.

Does it just relate to the risk of damaging the surface of a mirror, compared with the possible damage to a camera lens? The same 'optics' operates in all imaging systems. Does anyone have a reference to measured effects of surface contamination of lenses and mirrors?

[Singlin]

I clean mine regularly.

Distilled water is difficult to find here.

Ionized or demineralized is not the same and leaves streaks.

I import distilled water from the UK with a lab certificate, My mirrors dry completely spotless.

[iapa]

I seem to remember, decades ago, that my parents use ice from the freezer to top up lead acid batteries (car) and in the iron on the basis that it is effectively distilled as it was just the water in the air freezing so no contaminants.

This was in the days long before self defrosting ridges and freezers - so, may not be a source nowadays.

Air was cleaner then too

[Alien 13]

I used to clean my old Charles Frank reflector mirror every month with some of the mild green stuff and a final rinse in distilled water that was freely available in the good old days and never had an issue, I am sure the contaminants in today's atmosphere will do far more damage than a wash.

Alan

[John]

1 minute ago, Alien 13 said:

I used to clean my old Charles Frank reflector mirror every month with some of the mild green stuff and a final rinse in distilled water that was freely available in the good old days and never had an issue, I am sure the contaminants in today's atmosphere will do far more damage than a wash.

Alan

Every month ?

My 12" dob has had it's mirror washed once in 18 months.

I tend to agree with this from Alan MacRobert of "Sky & Telescope" magazine:

"A dirty lens or mirror can always be made clean, but a scratched one is scratched forever. Cleaning causes tiny scratches, or sleeks, if you don’t do it right, and maybe even if you do. A few sleeks don’t matter, but a lot of them will. So clean your optics rarely."

Practically every piece I've read on this seems to discourage over-regular mirror cleaning. Perhaps they are all wrong though

[Jonk]

I really want to clean my 16"but would probably have to do it in the bath!

What's stopping me is the fact that although reasonably 'dirty' to look at head on, I don't think it would make much of a difference if I did clean it and I risk damaging it.

I've cleaned 6", 10" and 12" mirrors in the past but these were relatively cheap mass produced ones, but easy to do correctly.