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Hi there,

While collimating my telescope this afternoon I couldn't help noticing that the surface of my primary is absolutely filthy. There are all sorts of stuff on it, dust, fluff and a few bigger lumps of dust. What I'm wondering is if it is possible to instead of fully cleaning the mirror, to brush or blow of the surface stuff using either a small blower or the brush that is on the end of my Celestron LensPen?

If it does end up needing a proper cleaning, would I have to use strictly distilled water or would de-ionised be ok? Distilled water is pretty hard to get hold of and quite expensive. I've heard that the difference is that distilled has been evaporated and then condensed and this removes all traces of organic and mineral contaminants. Deionised is merely filtered and leaves in organic contaminants but is free of minerals.

Also what is the chance by washing that the centre collimation spot will drop off, I've heard it happen to someone else on another forum?

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Disteilled water is cheap as chips - have a look on ebay. There are plenty of people selling lab quality distilled. A friendly phramacy can probably get you some as well.

A blower might remove some of it but I;d not put a lens pen on the mirror myseld, too great a danger of the lens pen pushing drek across the mirror face and causing a scratch.

Centre spots can fall off - they arent hard to replace though - if you want a quick guide I have one online - its not finished yet so there are typos aplenty.

take a look here Cleaning the Telescope Mirrors

Distilled water here on ebay Distilled Water 2 x 500ml on eBay (end time 12-Jun-10 02:25:09 BST)

You only need about 200ml to flush a mirror with.

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Relevant question here:

What exactly is di-ionized water?

I am thinking that it is simple tap water that has been boiled (and left to go cold) to remove any heavy metals/organics?

My primary is fine...............a few hairs and stuff that easily blow off using my rocket blower. My secondary mirror has a few small water marks on it that need wiping off. They are small and dont seem to cause a problem but they annoy me just knowing they are there. I have a lens cleaning kit for my camera and i think if i gently rub the secondary with the tissue paper in the kit that all will be well. However it could just rub the marks all around and make things worse. I certainly aint gonna use the liquid cleaner provided in the camera lens kit.

Edited by LukeSkywatcher

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Thanks for the quick reply.

In regards to the Lenspen one end has the cleaning element, some sort of cleaning solution in pen-like tip and the other end has a soft brush for brushing away larger bits of dirt.

I've bought a pack of that water so now to wait for that to arrive. The brand of soap flakes mentioned in your guide are they the ones I should buy or would these be ok?

Granny's Original Pure Gentle Soap Flakes 425g on eBay (end time 12-Jun-10 11:28:15 BST)

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I would use the pen cleaning device for obvious bits of stuff on the mirrors.

However you can clean them quite easily yourself using nothing more than warm water, washing up liquid and a nice soft towel.

Simply remove the mirrors, wash them under a shower head in a warm water, then apply a liberal amount of washing up liquid and rub gently in circular motions the mirrors to remove obvious areas, you shouldn't press too hard obviously but hard enough to feel the dirt come away with your finger tips.

Wash your hands off then tilt the mirror and wash off the excess liquid, then maybe repeat again to get the clarity your after, the running water should show any sticky areas, then leave in a stable are on its side and allow the mirror to semi-dry off naturally for about 5 minutes or so, when you come back you can place the mirror surface down on the soft towel...beware not to rub the mirror or move the mirror when its on the cloth as you can scratch it. After a few seconds pull the mirror directly up and the water marks should have gone.

You should now have a shiny looking mirror.

You can use distilled water if you like, its maybe preferable for the rinse section.

(please note, this is only a way I found from the internet, if you don't like it don't do it, worked fine for me though.)

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Well using plain old washing up liquid would save me a bit. I have seen a few other web tutorials mention using it so it can't be that bad fr the optics.

Just the centre spot to worry about, where can I get that guide for placing the spot printed on plastic?

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LukeSkywatcher. Please don't use any tissues to clean your secondary, very likely to cause scratches. Clean this mirror the same way as you would the primary. Hypernova. Go easy on the washing up liquid, it is very concentrated for this purpose and can leave smears. Much harder to rinse off than soapflakes.

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Disteilled water is cheap as chips - have a look on ebay. There are plenty of people selling lab quality distilled. A friendly phramacy can probably get you some as well.

...

Distilled water here on ebay Distilled Water 2 x 500ml on eBay (end time 12-Jun-10 02:25:09 BST)

You only need about 200ml to flush a mirror with.

If you read the description on this Ebay site, it is actually deionised, not distilledf water...

It is pretty hard to find cheap distilled water.

Having said that, I have always used deionised water (for car battery from Halfords or other auto shops) for the final rinsing without a problem.

/callump

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LukeSkywatcher. Please don't use any tissues to clean your secondary, very likely to cause scratches. Clean this mirror the same way as you would the primary. Hypernova. Go easy on the washing up liquid, it is very concentrated for this purpose and can leave smears. Much harder to rinse off than soapflakes.

The tissue i have is kind of like blotting tissue/grease proof paper. Its FINE for cleaning camera lens/binocular lens/Refractor lens..........i have not used it on my reflector mirrors.

Thanks for the warning.....................i will NOT use it on my mirrors.

It has not scratched my camera,bins,refractor but i guess reflectors are more sensitive.

Edited by LukeSkywatcher

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Distilled water ......I just pitched that one up as it was the firts one - distlled water is cheap honest. Mine states its 99% pure and I can swear to the fact it left not a single stain on the mirror after washing up.

Tip for the soapflakes - add the flakes to really hot water to make them froth up then cool the water down before the mirror goes in. Pure soapflakes need quite hot water to get them to dissolve. They also dont lather up as much as stuff like Fairy Liquid.

Soapflakes - doesnt matter overmuch so long as they are pure soap. What you dont want is bleaching agents or silicon additives.

Centre spotting template is here http://www.catseyecollimation.com/15in%20Max%20Template.pdf

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Thanks Astro Baby, how do I go about getting that template printed on to plastic sheeting?

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Ahhh - depends on your printer - mine does printing onto plastic 'foils' what some people call transparancy paper.

If your printer doesnt hack it send me your address by PM and I'll mail you one run off on my printer.

Strictly speaking you dont need transparacy - you could print onto plain paper or card and just cut out a few sections so you can cee alignment between the mirror and the lines on the paper.

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De ionized water isnt boiled, i make it for use in my marine fish tank as you need pure water to start with before you add your salts.

Its passed through filters, typically a carbon block, then a microfilter, then through a membrane and then through some DI resin, this produces pure water, you can use heavy metal filters to make it a 5 stage process aswell

De-ionized water should have a TDS (disolved solids) of 0 meaning its pure

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Well I've had a crack at cleaning the mirror having received my distilled/de-ionised water this morning from ebay. In all I think the cleaning has done its job, most of the surface contaminates have disappeared off the mirror and it is now drying off after being rinsed off with the water.

One issue though the appearance of a small splodges all over the mirror in a even coat, very small they are and I can't tell if they are dust/residue or the aluminium coatings of the mirror, can someone help me with this? I can't post a piccy as don't have a camera at the moment.

P.S i haven't had a problem with centre spot, it has stayed thoroughly stuck the mirror throughout the cleaning process :D

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proper medical grade cotton wool (not the cheap make up remover stuff) is good for cleaning, but get rid of dust first as it has sharp edges... i used a very small amount of mr muscle window and mirror cleaner on my primary with no adverse effects after a session in a field (pollen everywhere) i noticed afterwards there were no streaks whatsover unlike the really small ones you can get occasionally with deionised water. Very shiny surface too

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Hold the mirror up to the light and look through the back surface, if the spots are imperfections in the coating you will be able to see the light through them.

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De ionized water isnt boiled, i make it for use in my marine fish tank as you need pure water to start with before you add your salts.

Its passed through filters, typically a carbon block, then a microfilter, then through a membrane and then through some DI resin, this produces pure water, you can use heavy metal filters to make it a 5 stage process aswell

De-ionized water should have a TDS (disolved solids) of 0 meaning its pure

Thanks. I had a hunch i was wrong about it.

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These are the imperfections that I am seeing on the mirror surface, they are auite difficult to image as the camera wants to focus on the image reflected by the mirror rather than the mirror itself.

post-17251-133877454836_thumb.jpg

post-17251-133877454844_thumb.jpg

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Hi Tom. You seem to have done a pretty good job of cleaning the mirror but its still a bit messy with whatever those thousands of specs are. They cant be dust because they would have cleaned off when you cleaned it (not to mention that they dont even look like dust). They certainly are not normal for a mirror and should not be there. To me they look like residue left over from having been in the same room where someone sprayed air freshner or something silimar like fly killer etc while the mirror was exposed to the open air.

I dont think they will harm the mirror or even show a marked loss of quality of image but i would certainly have another go at cleaning the mirror.

Was the mirror in that condition when you bought the scope or is it just after using it for an amount of time since you bought it?

Edited by LukeSkywatcher

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TBH I don't know if it was in that condition when I first used it, last september. I have only noticed them from december onwards so I am unsure if it has been something that has happened in the house that has caused it. Up until april it was stored in my bedroom and always had the dust cap on the top but I did sometimes neglect to fit the cap for the eyepiece adapter so something may have drifted in through that?

I can tell you though that those specks are absent where the mirror clips are in place so I am assuming something has settled on the surface.

I am wary of overcleaning the so as to damage the coatings but I'll give it another try tomorrow maybe using some running water such as the shower at least once to see if that makes a difference. I also need to get my hand on some surgical cotton wool to rub the mirror if those specks refuse to budge, there might some in the first aid box somewhere.

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Probably a completely wild and out of the ballpark thought here, but you don't think it might be the result of volcanic ash settling on it do you?

That fine stuff can have all manner of nasties bonded to it, which might react with the coatings?

Obviously, I hope I am wrong . . . . . .

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The most my primary has had to deal with since mid december 2009 is the odd flake of skin or eyelash. There is a couple of minute water marks on my secondary but they dont mess with the image so i am not gonna try to remove them.

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Those pics dont look good to me. You havent been splashing the talc powder around ? Did you use soapflakes & maybe not dissolved enough?

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I use the shower idea because our 20 inch mirror takes a bit of space. I get the shower to ambient temperature (ish) then tip the mirror to an angle and play the water down the surface for quite a while to rinse off any bits. I then let it soak in water with a truly miniscule amount of detergent added. I try not to wipe it but, if I have to, I use CURVED strokes. This is most important because a curved scratch will not show, not that I have ever scratched it... so far! After that more shower and then a final rinse in distilled water.

I have done this every year since buying the telescope and it is doing fine.

As for the centre dot, all I did was make a 20 inch diameter paper circle, fold it into quarters, cut a hole in the middle and use that to show where where to put on a ring binder reinforcer. Surprizingly this has now had at least five showers without disappearing.

While I would advise caution and a light touch I wouldn't get too hung up about this task. The worst bit is lugging the big mirror. Whoops, tinkle...

Olly

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i used the soapy warm water and shower,then let it dry naturely.

it left a few water runs and would have been better using a hairdryer.

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