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Mirror scrub

thing

By thing
in DIY Astronomer

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thing

thing

Posted
Posted

Have just wire wooled my primary........ :shock: no not really I followed the advice given here. The wash went well but how do you get rid of the dried water marks? I rinsed the mirror in filtered water, would distilled water be better? Also do you let it dry naturally or use a hair dryer on cold?The mirror was far better even with the water marks, which aren't noticeable once it's installed. The other thing was, after I collimated the mirror I managed to get a quick peek at Deneb through a gap in the clouds and although the Airy disc at defocussing was nice and centered, there was a tiny bite size chunk missing out of it, defocussing the other way added a tiny chunk to it. Anybody any ideas? The seeing was bad, I was looking through cloud and it's very murky anyway but that shouldn't effect it should it?

In case anybody is wondering why a washed a mirror that was about a month old, you should have seen the amount of black paint flecks that had stuck to it after falling off various bits of the scope.............wonderful quality control from C******** there then.........

I was surprised by how painless it was, if anybody can come up with a way to get rid of the water marks it wouldn't bother me doing it again.

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barkis

barkis

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I hope you did not use washing up liquid in the water you washed it with. If the stains are bad, then it might be wise to do it again. The other bit about final rinsing, you should do it with de Ionized water, and do it a few times. If the mirror has been cleaned well, and rinsed with distilled water, standing it on it's edge, should see most of the excess water run off. Any persistent globules can be picked off with the corner of a tissue. It will pick up the water without touching the surface. The bit about your shadow on the mirror I answered in your other post.

From your description here, it sounds like your focuser is getting into the lightpath. When you look at a star again, use a low power eyepiece, and don't stick it right into the focuser. Just insert about halfway, and see if the shadow goes away.

Ron. :rolleyes:

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thing

thing

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Incidentally, are there any other people here who are incurable messers-about-with-things? The first thing I have to do if I buy something new is take it to bits to see how it works.......and see if I can improve it :? It drives my wife mad. Or madder anyway.

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barkis

barkis

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I wouldn't go to Halfords, try a Pharmacy, they will probably be cheaper. Or, you could try a Kwik Fit Depot, if they do a lot of battery charging, they may have it in large plastic drums, and they might sell you a gallon for a pittance.

Only a guess mind you. :rolleyes:

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blinky

blinky

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I would suggest rinsing it with Isopropyl. It repels water (for want of a better phrase) and evaporates leaving no marks as long as you get the 99% stuff. Have a look on Ebay there are a few folks selling very high purity Isopropyl for a good price.

I have not yet cleaned my mirror but when I do I will be doing the final rinse with this.

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peeceeTal2M

peeceeTal2M

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I totally agree with Blinky use 99% pure isopropyl alcohol, i got mine from ebay seller mistral_ie and it was less than a tenner, my local chemist quoted £200 for 2 liters!! Just do the final rinse with the alcohol and let it evaporate away.

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thing

thing

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Just ordered 5 litres off e-bay for 17.99 including postage. So you do the wash in the sink bowl with a tiny bit of hand wash then would you go straight for the isopropyl rinse or rinse it with water first? How many times would you do the isopropyl rinse?

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MikeD

MikeD

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Hold on all this talk of using isopropyl alcohol to clean mirrors has me worried. :shock: I always thought it was a no no to use isopropyl alcohol

See this quote from this sitehttp://www.astro-tom.com/tips_and_advice/cleaning_optics.htm

If you are cleaning a Newtonian type reflector you will be cleaning your primary and secondary mirrors. If they are aluminized mirrors (most are) do NOT add the isopropyl alcohol in step 3, below because alcohol reacts with aluminum.

Has anyone used isopropyl alcohol on a mirror with no side affects?

I always use tap water running over the tilted mirror while dancing a cotton wool ball over the surface (no pressure just the weight of the water logged cotton wool) and a good final rinse with Distiled water.

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FLO

FLO

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I have used an Isopropyl/distilled water mix to successfully 'spot-clean' stubborn marks on a mirror but agree that it is not normally wise to use anything other than soft or distilled water with some mild detergent, followed by a rinse with fresh water.

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thing

thing

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I have used an Isopropyl/distilled water mix to successfully 'spot-clean' stubborn marks on a mirror but agree that it is not normally wise to use anything other than soft or distilled water with some mild detergent, followed by a rinse with fresh water.

It's the rinse with fresh water that is the problem though, the mirror is spotless after I've cleaned it, rinsing it with fresh water adds all sorts of water marks.

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barkis

barkis

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If you are talking about fresh water as out of your tap, there is nothing fresh about it. It is full of all sorts of minerals + lime. It will leave stains when dried. I would not touch a fine aluminium coating on an astronomical mirror with anything other than water. No Isopropyl, and certainly no Washing up liquid, no cotton balls, nothing. Clean it by sluicing, or immersing in tepid water for a short while. Then rinse it thoroughly with distilled water, stand on it's edge to dry. An aluminium surface starts to oxidise from the moment it is deposited on to the glass. After a while this oxidised layer offers a modicum of protection. This layer can have a milky appearance but is of no detriment to the mirrors performance.

If you are tempted to rub it clean, however gentle you think you are, you will put minute scratches on the coating, and these are far worse than an irritating stain that might persist after cleaning. As long as you get most of the gunge off with water cleaning. Let it be.

Ron.

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FLO

FLO

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... soft or distilled water with some mild detergent, followed by a rinse with fresh water.

... the mirror is spotless after I've cleaned it, rinsing it with fresh water adds all sorts of water marks.

I must have been ambiguous, I meant fresh soft or distilled water.

Here in Exeter our tap-water is soft so doesn't leave smears the way hard-water does. If you live in a hard-water area then as Ron says you will need to use distilled water.

HTH

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