Question about Newtonian Primary mirror washing

[N3ptune]

Hello I was wondering about the clean-up of my primary mirror but I am confused seriously and some people succeed in scaring me with that. (it's for my SW 200p Newtonian)

):

I read this first: For a famous astronomer in Europe, it's good to wash the mirrors more often to prevent hard accumulations on the surface making it easier to wash each time. And to him washing the mirror properly won't scratch it plus it's going to prevent contaminants from eating the aluminium.

Really nice procedure here in French:
http://fredburgeot.fr/Nettoyer%20son%20miroir.htm

My telescope is 4 months old right now, I went out maybe 12 times outside with it, it does not required to be washed right away, it's still pretty much ok. So in my mind I had something like 1 or 2 cleanups per years. (Total cleanup of the mirrors with distilled water and the required procedure.)

But another person said to wait a minimum 1 to 2 years before washing the primary and secondary because my instrument is new and the aluminium finish takes 1 to 2 years to cure solid on the glass. Also, each washing will remove 5% of the reflectivity according to him, (which is a LOT to me.) <--- I tend to be skeptical a little bit about the 5%

It's one voice against another really..

What do you people think about all that ? is one clean-up per year too much? What do you do?

Thanks

[brantuk]

Primary mirrors have to get pretty bad with thick dust before they need a wash. Twice yearly sounds a bit much to honest. I did my 12" once in 3yrs of ownership and that was only to make it pucker for selling on - or I wouldn't have bothered cos the views were fine.

[niallk]

I'm probably not a good example: I must have my SW 250px 7yrs or more, and I'll give its mirrors their first wash one of these days... really only as a practice run for cleaning my 15".

I kept reading that if I was still getting great views, then its fine, even if it looks dusty with the odd dew blotch! The views have just kept getting better as I continue to learn to see more.

I am however considering giving my 15" a wash every year or so ... it might get its first wash in the next few months. It is more exposed, and has had some dewing incidents.

[John]

I've done my 12" mirror once in 2 years. It might need doing again in another year or so.

 

[laudropb]

The general consensus is to wash only if the views have deteriorated. Had mine for 2years and still see no need to wash.

[N3ptune]

ok

They have to get really dirty in order to wash them, my mirror is in the bottom of the tube so it's protected in a way, ill see it's condition after 1 year or more, I have no issues right now with visual quality.

Let's say it would be required to wash it once per year or once per 2 years, should I fear to do that?

Did anybody ever noticed a reduction in reflectivity after a few washes?

--> I am trying to gauge how much washes a typical mirror like mine can handle before it needs recoating. Maybe cleaning it properly isn't the reason why one needs to do a re coat on his mirrors either.

 

 

 

 

[ollypenrice]

My 20 inch lives year-round in a drafty roll off and will certainly NOT be cleaned more than once a year. This policy has seen me happy for ten years without ill effect.

Olly

[Charic]

Mine was new as of 2013 and its had one clean since, not really a wash, but a clean using  of all things, windolene, I just stripped the scope down to see how it functions and fits together and cleaned the mirror prior to re-assembly?
Its not suffered in anyway,  that I can see, and  still looks perfectly good to this day. I also totally enclose the scope in wraps, a cotton sheet, plastic over sheet  and kept  inside a cupboard, effectively keeping the scope as clean as possible.

Windowlene (the 4-1 blue solution) is not the recommended or prescribed solution for cleaning your optics, I just wanted to experiment, and I know how streak free and clean  it leaves normal glass,  It  does not appear to have affected the  mirror in any  way whatsoever!

I do intend to change the centre spot this Year to something smaller, as the original came loose. I also like those spots that  look like a  trefoil?

[brantuk]

Washing a mirror wrongly and unnecessarily should be feared more than the frequency of washing. If done right it needn't be anything to fear - but the more you do it the more you increase the chances of goofing it up.

Think about what has happened to it and what you are doing to clean it. Over the course of time dust will settle and water marks may appear from dew and drips. The the particles you want to remove will be dragged off the surface leaving hairline scratches in the coatings. Once these go through between the mirror and it's coatings, then any subsequent water ingress will result in eventual mould and peeling. This may be quick or slow, and take months or years:

Here is the procedure I used - I've only done it once on one scope in 8yrs - worth bearing in mind:

 

 

[N3ptune]

Ok,

Looks like a mirror can last a long time after all. I am not going to wash mine for nothing has suggested here.. and keep the instrument in a dust safe storage environment. 

I liked the video too thanks for sharing it, this technique is really simple and et looks really effective, contacts with the aluminium is reduced to the minimum. 

1 wipe per towel with no pressure, I like that, this should do a good job I am convinced.

((:

Looks like he's using good quality dish soap there, it doesn’t look like I can get any Windolene products in Canada. Any dish soap can do?

 

[brantuk]

Steve is using pure soap - something like a drop of Fairy Liquid - he's actually a member here - "Steppenwolf" author of "Making Every Photon Count" (the astro imagers bible).

[barkis]

I was made aware some time ago in a book on telescope making, that liquid detergents can contain a mild acid.
Of course I think any damage to coatings may only result if the method is used very often, and not after a 
one off process.
I subscribe to the popular view that mirrors have to be pretty grimy to warrant washing, and should
only be cleaned if that is the case.  The surface shouldn't be touched by anything other than water.
Soaking in a  tepid water bath containing soap flakes should suffice, perhaps two or three times
if required.  A final wash down with   deionised water,  and stood on it's edge to drain off surplus water.
any remaining globules can be carefully picked off with the corner of a Tissue. Do not be tempted 
to remove any marks by rubbing the coating. however lightly you think you might be applying pressure.
you could still sleek, or put minute scratches on the mirrors coating, which can cause light scattering.

I know many mirrors have protective coatings applied, however, I would still not risk contacting the surface.
 

 

 

[N3ptune]

Honestly I am not really afraid to pass a soaked microfiber towel with no pressure on the mirror has shown in the video. The mirror was in the water for a few minutes so everything there should be soft.

I looked at the various soaps, I can get the Fairy Liquid in Canada, the original formula has the link bellow:

http://www.amazon.ca/Fairy-Original-Washing-Liquid-433ml/dp/B00MYA36GO/ref=sr_1_1?ie=UTF8&qid=1455639202&sr=8-1&keywords=Fairy+Liquid

For the soap flakes I called a local soap specialist and they don't have flakes but she said I can grate a bar of the following soaps.

CASTILLE SOAP: Looks like the flakes comes from this one.
http://puresoapflakes.com/
What are Pure Soap Flakes? Pure Soap Flakes are small, translucent, crystal like, silky flakes of pure castile soap concentrate that are saponified from a signature blend of pure coconut and soybean vegetable oil. They are the mildest of cleaners and free of injurious bleaches, chemicals, dyes, enzymes, GMOs, perfumes, phosphates, sodium lauryl sulfate, or synthetic surfactants. Pure Soap Flakes are kind to people with sensitive skin and senses, pets, natural fibers, and woods.

https://en.wikipedia.org/wiki/Castile_soap
Castile soap is a name used in English-speaking countries for vegetable oil based soap made in a style similar to that originating in the Castile region of Spain.^[1] Traditionally made with olive oil, it now may be used for any hard, white, vegetable-based soap.

On amazon.com they have pure soap flakes from England, it looks like the right thing but I am sure  it's not possible for me to order the bag, no distribution in Canada. I would trust a soap like that for my optic.

http://www.amazon.com/Dri-Pak-Soap-Flakes-454g-bag/dp/B004SV0A3E
They are made of 100% vegetable material and degrade harmlessly after use. <-- Looks like Castille soap

http://soap-flakes.com/purchase.html

ALEPPO SOAP:
Aleppo soap is classified as a Castile soap as it is a hard soap made from olive oil and lye, from which it is distinguished by the inclusion of laurel oil.

Traditional Aleppo soap is made with 100% natural, olive and laurel berry oils, water and lye. The relative concentration of laurel oil (typically from 2–30%) determines the quality and cost of the soap.

MARSEILLE SOAP:
Traditionally, the soap is made by mixing sea water from the Mediterranean Sea, olive oil, and the alkaline chemicals soda ash (sodium carbonate) and lye (sodium hydroxide) together in a large cauldron (usually making about 8 tons).

BLACK SOAP: This is not working for my mirror.
It is also used to lightly exfoliate and give you healthier looking skin.

==================

Quite a bit of information on soaps.

[ollypenrice]

25 minutes ago, N3ptune said:

Honestly I am not really afraid to pass a soaked microfiber towel with no pressure on the mirror has shown in the video. The mirror was in the water for a few minutes so everything there should be soft.
 

The soaked microfibre cloth moving across the surface is not the problem. The problem is the potentially abrasive particles now residing on the microfibre cloth. You are cleaning the mirror because it seems to have particles on it... I would rather soak them/rinse them off without solids in contact.

Olly

[N3ptune]

Just water may leave a film on the mirror also, could a few invisible micro scratch be worst then a film on 100% of the surface?

That's one question.

I don't get really happy with the idea of washing once per 3 - 4 years or more, even 2 years. Because I think the build up film can become hard to remove. And this could do more harm and pain then a preventive wash once per year or 2, if visually required only.

The same has a dirty car using a no contact car wash, the film won't come off so one way or another eventually, it will need a surface contact with a glove to wipe off the film, there is no other way that I know of doing it.

(I may be wrong about buildups here, it's only speculation)  

 

[ollypenrice]

It's easy to look at an optical surface, be it a lens or a mirror, and see 'smears.' A very fine film on the surface. You can see it because it affects the tiny amount of light reflected from a lens or misdirected by a mirror - but it is totally unimportant. The professionals can clean surfaces without causing this effect and that's nice - but of no importance. You might see a fingerprint on a corrector plate or lens. The amateur thinks this is a disaster. The professional knows it is insignificant.

Olly

[N3ptune]

Olly ok, i keep your advices in mind.

--> The fun part is that I will have to make up my mind someday with a load of conflicting informations, fortunately I can have a lot of various opinions on the subject from professionals and non professionals.  The guy on the first link posted, message #1, may very well be a professional too but he's totally saying something else.

But it's not a contest, it's a study.

Olly, what about the soap? what brand do you use?

[ShrewView]

I'm also thinking of cleaning my mirror.

I was planning to go for the soak with a little soapy water and then rinsing with clean tap water and then finally deionised water.

As for how often to clean it? I've always tried to keep the dirt out in the first place by capping the scope and covering it when not in use, but even being careful it does get in eventually. Still this will be the first time in over 20 years! 

At this rate another couple of washes will get me to the point at which I'll be past caring the next time its due

[N3ptune]

20 years Holly!

You might pass away before your next clean up shrew. (hehehe) I wish you luck with that. (the wash up)

====================

- Do you people think 1 wash can remove 5% of reflectivity each time. Can this statement be true? <-- A men told me that.

- I don't know the purpose of the coating on my mirrors, does this factory coating is applied on the sole purpose of getting me a better view suppressing reflection or is it protecting the aluminides too (or maybe both. ?)

--> I heard that when they redo a mirror in a craft shop, they don't put a special coating on the new aluminide like the one from the factory. The reason for that (has I read): The coating makes the mirror less effective, apparently.  Now if the mirror is less effective because of the coating, what's the purpose of that coating?

That's beyond my understanding. 

- Another men tells to wait 2 years before I can wash the mirrors. I can't undo this input, can this statement be true?

[brantuk]

"can remove 5% of reflectivity each time"

Yes you can - you can also wash 20% off or 1% or 100% off - depends on how much gunge you have on the mirror and how hard you press on it - unless you have lab controlled conditions and take accurate measurements and tests you're never gonna know.

"purpose of the coating on my mirrors"

Anti reflective coatings - maybe other reasons too - but you don't want the full reflection from a mirror bouncing round inside the tube wrecking the view.

"wait 2 years before I can wash the mirrors"

This is a purely arbitrary figure and would be entirely circumstantial. Don't forget - the scope will be used on clear nights only when you can see the stars. It's not as if you're gonna be observing through a sand storm every time.

Honestly N3ptune - and with all due respect - you're worrying unnecessarily. You have enough info here in the thread now to choose when and how to wash your mirror, and how to judge if and when it's needed. I would add - there's some very experienced and knowledgeable folks here who have all offered sound advice and I don't believe anyone of them would put you wrong. Hope I've helped too

 

 

[N3ptune]

I don't doubt the experience of people here, this was rewarding for me this discussion. I know almost all I need to know in order to do my things right.

I am understand things from A to Z to a point where I won't have any more questions, that's all.

--> My telescope seller he told me things, now, does he wants me to keep my mirror many years or he wishes to sell me another mirror soon? I will never know but I can ask questions to give me more leverage, these guys are professional sellers and they are great. 

I am dealing with professional advices here.  

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Quote

Yes you can - you can also wash 20% off or 1% or 100% off - depends on how much gunge you have on the mirror and how hard you press on it - unless you have lab controlled conditions and take accurate measurements and tests you're never gonna know.

Definitely in my imagination I saw the technique from your video, I was not precise enough.  Based on that video, would you think something noticeable would come off? (Me I don't believe right now even 1% of the mirror came off after the end of this video)

Quote

This is a purely arbitrary figure and would be entirely circumstantial. Don't forget - the scope will be used on clear nights only when you can see the stars. It's not as if you're gonna be observing through a sand storm every time.

I have that in mind always, and even further, if in 3 years my telescope is still clean, I am not going to wash it for nothing, has learned here.

 

 

 

 

 

 

[jetstream]

I like a clean mirror. Some stuff such as pollen and some dusts will make a substance that can eat the coatings if the mirror is "fogged" up repeatedly with dew or frost. I was told that the trick to make coatings last is to ensure the mirror is kept dry. If it fogs up a lot,make sure its clean or the junk can eat the coatings.

[N3ptune]

Jetstream, I agree with that.

I am looking forward to prevent such attacks.

 

[niallk]

4 hours ago, jetstream said:

I like a clean mirror. Some stuff such as pollen and some dusts will make a substance that can eat the coatings if the mirror is "fogged" up repeatedly with dew or frost. I was told that the trick to make coatings last is to ensure the mirror is kept dry. If it fogs up a lot,make sure its clean or the junk can eat the coatings.

This is why I'm considering a wash every year or so for my 15" mirror: and not leaving it 7yrs and counting like on my 10"

[ultramol]

I found the scariest thing about washing the primary mirror was how tight to put the clips when reassembling. My mirror moved in its cell the first time I did it because I was tentative with the screwdriver. Had to take it back out and nip them up a bit more.....