So you need to wash a 12" mirror?

[Gargoyle_Steve]

I've previously washed the 12" mirror from my GSO dob in the kitchen sink but have never felt good about this arrangement. With things like the sink being too narrow for the mirror assembly to sit flat, the risk of oil/grease/food particles remaining, etc, and especially the fact that the sink is NOT portable, I've been looking for a better, and preferably inexpensive, solution.

Last week I found it, courtesy once again of Bunnings Hardware.

Let me say first that if you want to wash one of these 12" mirrors the cage assembly has an outside diameter of 350-355 mm's, and while that doesn't sound like a lot I can assure you that finding something large enough to accomodate that laying flat, let alone the extra inch or so needed to get your fingers in to pick the mirror up again safely, IS quite a task!

I've even measured typical outdoors "plastic" rubbish bins, but like most objects I tested the internal taper means that by the time you reach bottom they simply aren't wide enough. I looked at several plastic solution, up to and including $30-40, none were big enough


This is a Bunnings "Multi Purpose tub", a solid, sturdy plastic tub that has an excellent design, strong rim, and well designed rope handles. I found these on display at the end of an isle. They come in 4 colours (red, blue, white and black) and 2 different sizes.

This is the larger one: 58 litre capacity, 350 mm high, it's interior base diameter is 440mm with a raised "ring" at around the 350mm size that supports the GSO mirror frame perfectly, even letting you get your fingers in under the edge to get a good grip!

Best thing of all - it only cost me $11.48, the smaller size was under $9 and is probably suitable for 10" or smaller mirrors.

The only problem is that it is very deep, I plan to cut the lower section off at approx 1/3 height, and hope I can cut out the handle sections and attach them onto the remaining base section. I'll let you know how it goes.

[astro_nutt]

Great idea Steve!..I've been having a few concerns when I wash my 10" mirror in the laundry sink..even though I remove all the soap etc as best I could..then give it a go over with metho..I still feel that some oily residue will deposit itself on the mirror..( as I think is the case with the faint swirl-like pattern that is currently on the mirror!..but it hasn't affected the image quality thank goodness!!)..so I might invest in a tub solely for that purpose...thanks again Steve.
Cheers!

[Dez]

G'day Steve

Nice find mate and thanks for the info. While my telescope is very new still and will hopefully be some time before needing a clean, I always seem to look down the tube at the end of the session with a sense of fear, expecting to find something stuck to the mirror...

I'm still dreading the day I'll need to clean the mirror for the first time, but your tub suggestion seems like a cheap and practical option

Cheers
Dez

[iceman]

Good idea! My 12" is too big for the kitchen sink too, very annoying!

[ngcles]

Hi All,

I hate washing mirrors. I mean I really, really hate it. It almost appproaches a phobia.

Even after all these years I am gripped by a morbid fear that something will go wrong -- horribly wrong. I wait till either everyone is out of the house or asleep so there are absolutely no distractions. I only relax when it is back in the ''scope or safely boxed.

My 12" just fits in the kitchen sink -- get a bigger sink guys!

The 18" is a different problem -- it gets done in the bath! It is the only thing that ever gets washed in the bath as we are all shower users. Does use a fair bit of water though.

Hint: As the last step rinse the mirror in isopropyl alcohol -- buy a bottle at the chemist for a few dollars and squirt it on liberally. It breaks up the water and removes it quick, then dries much quicker than water and leaves no residue or swirls on the face of the mirror.

Make sure it is _pure_ isopropyl alcohol and does not have additives to soften hands etc.

Oh, and don't forget to take the rubber duck out of the bath ...

Best,

Les D
Contributing Editor
AS&T

[Dujon]

Some great hints in those postings. Thanks. There could be a decent article in there somewhere, Les.

I too dread the prospect of having to disassemble and clean my primary mirror. Although I have read that using distilled water is the way to go I have wondered if filtered rain water might be just as good. Then there is the cleaning itself; how is it done? Does one rinse the thing and hope for the best? If not, then what should be used to swab the mirror?

The mere thought of scouring it in some manner or other makes me go weak in the knees. Right, I'm off for a bit of a lie down.

[astro_nutt]

If my mirror looks dusty, i'll let it go for 12 months before thinking about washing it.
After removing anything above the laundry tub, throughly srubbing it, wiping it again with metho then drying it out with lint-free cloth, clean the plug or buy a new one. I'll then remove my rings, etc and use rubber gloves whilst handling the mirror, (in case of any oils, dead skin, etc), then fill the tub about a quarter with warm water...I then mix one drop of dish washing detergent in a cup of water, and use only one teaspoon of this and add it to the tub, allow the mirror to soak for about 10 minutes then drain, rinse in warm tap water then tilt the mirror and give a final rinse in distilled water, touch any large drops with the corner of a rolled up kleenex without touching the mirror. Whatever's left behind, if it's only a few specks can stay there..As I've learned if a mirror looks dusty when you shine a torch on it, there wouldn't be enough to cover the head of a pin!
The last time I tried this I had a piece of oily grit stuck near the centre of the mirror (which would have been in the shadow of the secondary and therefore won't affect the image) but I chose to remove it anyway for fear it could move, I did this by damping a corner of a rolled up kleenex with isopropyl alcohol and dabbing it gently 10 times..after about 10 attempts it was gone, another rinse in distilled water and presto!..nice and clean!
Cheers!

[ballaratdragons]

Les, I have tried many times at many Chemists, but I have never found a Chemist in Victoria that will sell it! I tell them what it is for.

A few years ago I also wanted to get some for cleaning a VCR head. The Chemist said to bring in the VCR and he'll put some Iso/Alc on a cotton bud for me and I had to clean the VCR in the Chemist shop :eyepop:

[Gargoyle_Steve]

As far as I know Ken you're right, it appears to be impossible to buy pure isopropyl alcohol anywhere these days, though you can get solutions with varying amounts of water and/or other additives. The best you can do purity wise is alcohol swabs, which are usually still only 95% or so pure, the remainder being water.

We used to try and buy alcohol liquid/swabs/patches, etc, for cleaning the heads on the large mag tape storage units years ago when I still worked for Telstra, this was back in the mid 90's. I remember one day another tech officer and myself were detailed onto ringing and/or driving to various supply places all around Brisbane, we still never found 100% pure alcohol.

[anj026]

I while ago now I bought some Diggers brand isopropyl alcohol in a little squirty pump bottle from Bunnings. It was around $10 for 125ml. I have been using it for cleaning eyepieces and objectives with no problems. It was near the turps and solvents section in the paint area.

[anj026]

I have just checked and it is on their website.
diggersaust.com.au

[Dujon]

Thanks, astro_nutt. When the time finally comes, and I'm inebriated just enough to pluck up the courage to meet the challenge, I'll try your method - though the dish washing detergent sounds a bit severe (in the sense of residual 'stuff'). The cleaning of the laundry tub also sounds a bit fraught so I might use your method but using Steve's tub . . . well, not Steve's tub, but one similar.

[Louwai]

Sholdn't distilled water be used for washing mirrors rather than tap water????

[iceman]

Distilled/de-mineralised water is used for rinsing, but you can use normal water for washing.

[iceman]

btw, there is an article here:
Cleaning the Mirrors of a Newtonian Telescope (http://www.iceinspace.com.au/index.php?id=63,345,0,0,1,0)

[GTB_an_Owl]

i had to ask my chemist a couple of times to sell it to me

he was a bit reluctant and had to check whether he could legally sell it to me (especially 500ml)

$32-95 for 500ml - 99.5% proof

geoff

[mlcolbert]

Guys, you can purchase ethanol in 20 litre containers from CSR. The catch is that you do need to be registered with the ATO. It is a simple matter of checking with them and down loading the application form as well as having a valid reason for requiring the alcohol. As being part research company, mine does so we are entitled to 250 litres per year. Cleaning is not a problem.

michael

[Dujon]

Thanks, Mike. Not that it makes me any less terrified of attempting the deed. Perhaps it's like many other things - in that the execution is easier than the period of pondering and prevarication.