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Cleaning my 16" mirror with "First contact"


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Hi Everyone,

After long hesitation and preparations, I have decided to clean the primary mirror of my 16" Lightbridge. Since the mirror is secured by 3 sticky rubber pieces on the side, I thought I will not take out the mirror from the holder, but I wanted to make a good cleaning after more than a year of gathering dust.

To minimize the chance of scratches or other surface damage, I decided to use "First contact", this forms a polymer film on the mirror and you can carefully tear it off when it dried. This film takes in most of the contamination from the mirror surface ( at least that is stated on the box ).

These were the steps i have done:

1. I have protected the center spot of the mirror by covering with a small plastic cup. The edge of it was already soaked in First contact and I let it dry, so this was certainly a "gentle touch" on the mirror. I have removed the 3 mirror clamps.

2. I took a large eough piece of plastic folie and cut a hole in it so that the mirror fits in this hole. I have secured the plastic to the sides of the mirror by tape. This way I don't spray the mirror cell, it would be difficult to take the plymer off from the inner side.

3. I have sprayed 3 bottles of First Contact liquid to the mirror in several layers, taking care that the edge gets more thick coating than the centre. This is very important, because you need to start "peeling off" from the edge. I waited 2-3 minutes between every layer, because than you get a stronger polymer film.

4. After 2 hours of drying time I took a deep breath and started to peel off the polymer film. There are special shaped peel-off sticker to do this as you see on the photo below.

The result is a perfectly clean surface, and I think I will do this again after maybe a year. I forgot to make a "before" image of the mirror, but believe me: it was really covered by dust.

I think the second time will be less scary :).

Cheers,

Janos

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Edited by jarbi
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Looks great but cannot see the benefit over warm water, a little washing up liquid and some IPA to stop it streaking.

Well done though you will see the benefit.

Thanks Doc,

I am curious if you have cleaned yours already, because than you had to "cut out" the mirror from the rubber protection. I was always wondering if that would be a risk.

cheers,

Janos

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Wow ! - that looks good.

You were braver than I was - I'd read stories of that stuff removing patches of coating along with the dust and debris so I chickened out and used warm distilled water and pure soap flakes. When I tried to remove my mirror (12" Lightbridge) I found that it was held in with sticky pads on all 9 of the mirror cell contact points ! - it took me ages to work out a way of getting it out of the cell !.

Good result though an thanks for sharing it :)

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Wow..what a good idea

It's been used at Keck as well modern liquid peel cleaning product, First Contact liquid cleaning solution, First Contact peel polymer, First Contact cleaning solution, First Contact Optics Cleaning, Mirror Cleaning, reflectivity

Impressive stuff, they even have before and after measurements to prove it, it works better than CO2

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Thanks Doc,

I am curious if you have cleaned yours already, because than you had to "cut out" the mirror from the rubber protection. I was always wondering if that would be a risk.

cheers,

Janos

No I removed the fan and kept the mirror attached to it's cell.

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The thing to note here is that you are not actually cleaning the 'mirror' but its silicon-dioxide overcoat (applied to protect the mirror from tarnishing). Some cleaning fluids can actually remove the protective coating! Baader Optical Wonder for example is not a good choice for cleaning mirrors for this very reason.

Personally I would have used water with a little mild soap, followed by a distilled water rinse. But it is good to hear you mirror cleaning method was a success :)

Not every manufacturer applies a silicon-dioxide overcoat, though they should. It is an expensive process that is sometimes omitted. All Skywatcher mirrors have the coating, as do the GSO mirrors fitted to Meade Lightbridge Dobsonians, but I once owned a Revelation Dobsonian (from the first series) with a GSO mirror that definitely did not have a protective overcoat. The mirror started deteriorating after only two years!

HTH

Edit: Just looked at the First Contact website - clever stuff!

Edited by FLO
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First Contact liquid...............

Thats the stuff that dries like latex? Seems like an ideal solution to cleaning. Looks like it did a GREAT job on your primary.

How did your primary become so dirty?

Paul,

I went to several observation camps last year with the 16" LB. The heaviest "impact" was the one in the Provence in september. I was there for one week, and there was really a lot of dust in the air at our place. I was delaying this cleaning action until now, but it became really necessary.

Janos

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The thing to note here is that you are not actually cleaning the 'mirror' but its silicon-dioxide overcoat (applied to protect the mirror from tarnishing). Some cleaning fluids can actually remove the protective coating! Baader Optical Wonder for example is not a good choice for cleaning mirrors for this very reason.

Personally I would have used water with a little mild soap, followed by a distilled water rinse. But it is good to hear you mirror cleaning method was a success :)

Not every manufacturer applies a silicon-dioxide overcoat, though they should. It is an expensive process that is sometimes omitted. All Skywatcher mirrors have the coating, as do the GSO mirrors fitted to Meade Lightbridge Dobsonians, but I once owned a Revelation Dobsonian (from the first series) with a GSO mirror that definitely did not have a protective overcoat. The mirror started deteriorating after only two years!

HTH

Edit: Just looked at the First Contact website - clever stuff!

Thanks Steve, it is a very important addition ! I am wondering if my mirror has this silicon-dioxide overcoat. I've read somewhere that you can see this overcoat as a blueish reflection when you look at the mirror from almost tangential direction. How can I figure it out for sure ?

cheers,

Janos

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I am wondering if my mirror has this silicon-dioxide overcoat. I've read somewhere that you can see this overcoat as a blueish reflection when you look at the mirror from almost tangential direction.

If it is a Meade Lightbridge then it will have the protective overcoat, it is the Revelation Dobsonians that need checking (mine was from the first series, I don't know about the most recent ones). The silicon-dioxide is sometimes visible as a slight petrol-blue colour. If the mirror has condensation on it then it is easier to see.

During winter, customers occasionally phone us after opening their Skywatcher telescopes concerned that they can see a blue cast on the mirror. It is only that the cold mirror has formed condensation when exposed to warm living-room air.

HTH

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Steve,

Thanks for the information about Skywatcher mirrors.

So you say that the mild soap wash method is suitable for said brand?

(Mine's due a clean :))

Lukeskywatcher,

I wonder if truss tube dob mirrors do get a little dirtier because the mirror is more exposed during use? Apart from dust particles in the air, I wonder whether fabric particles from the blackout cloth are to blame as well?

Edited by Beulah
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i used first contact to clean the main mirrors in my newise (which are glued in). I was by chance the first customer of the UK importer and so i got my kit for free, and the guy came to my house to help me do it!

It was really easy and it did remove every speck of dust, but it didn't get rid of water or grease marks. But i was advised to use acetone on these which worked very well.

The first contact dries on not like latex but more like polythene, it is not very stretchy really. But it came off in one piece and did not harm my mirror.

I don't have the newise anymore, and my SPX has a removable mirror so i will probably wash it in the sink - not sure about rubbing it with my hand though!

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interesting....

I guess if Keck use it and they advertise it for telescope cleaning, it shouldn't do any harm to mirrors... hopefully...

I've just done some googleing but can't find anywhere that sell this. Where can I get that in the UK?

Maybe FLO want to stock it? :)

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