Anonymous
Unregistered
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How about periodically blowing things off with compressed air (like for computers), to keep any buildup from possibly accumulating? Therefore no cleaning needed? (Or will it cause fine scratches from fast moving air)??
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rboe
Reged: 03/16/02
Posts: 63466
Loc: Phx, AZ
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I've heard pro and con regarding compressed air. While the source of the air can be suspect (say your handy air compressor used for your nail gun or staple: good way to contaminate your mirror with oil) the sheer pressure is thought to be a problem. Some recommend no more puffing than what those little squeeze bulbs can produce.
Frankly I don't have the patience for such a small puff. But shoving desert born dust across your corrector plate does have the potential of acting like fine sandpaper. Horrors! If only someone had written a doctorate theases on this very thing.
Good question: Comments?
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Ron
NS11GPS
Pronto
16" dob
127mm F9 Surplus Shed/Crawmach kit scope
Coronado SolarMax 40 on a Celestron 102 Wide Field
Best of ATM
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Anonymous
Unregistered
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Hi Ron,
You're right about compressed air. One time I had an air gun spew some fine oily mist on about 20 lenses being readied for coating.
I now use dry compressed nitrogen with the gun set at about 20 lbs. For blowing off water, I use about 60 lbs. That is to blow off water and not to let dry.
Al M
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rboe
Reged: 03/16/02
Posts: 63466
Loc: Phx, AZ
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OK, low pressure for particulates, higher pressure for clean mirrors with liquid on them. That makes sense. I had our conversation in mind when I mentioned the oil from compressed air systems - but didn't want to mention names 
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Ron
NS11GPS
Pronto
16" dob
127mm F9 Surplus Shed/Crawmach kit scope
Coronado SolarMax 40 on a Celestron 102 Wide Field
Best of ATM
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Mike Hosea
Postmaster
Reged: 09/24/03
Posts: 6148
Loc: "Metrowest" Boston
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Well, to answer the question, yes. You can do this if you have a good source of clean, compressed air (canned air products are no good for this because the propellant can spit). You can also put a vacuum nozzle near the mirror face and suck up dust without ever touching the mirror. However, what I think you will find is that over time, some dust is moistened by condensation and later dries. It gets a little bit "stuck" to the mirror so that at least a distilled water rinse is needed to bust it loose, if not a regular cleaning.
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Mike
- 7" f/6.7 home-built Newt and equatorial platform
- 120mm f/8.3 home-built grab-n-go Newt
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rboe
Reged: 03/16/02
Posts: 63466
Loc: Phx, AZ
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Mike, you ruined my plans! I was looking at getting a canned air product. I may have to go with plan B and get a scuba tank filled with CO2 (we use them to recharge our air pistols, get them filled at welding supply shops). Just need a regulator so 3000psi doesn't come out at strip the coating off on its' own accord!
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Ron
NS11GPS
Pronto
16" dob
127mm F9 Surplus Shed/Crawmach kit scope
Coronado SolarMax 40 on a Celestron 102 Wide Field
Best of ATM
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Mike Hosea
Postmaster
Reged: 09/24/03
Posts: 6148
Loc: "Metrowest" Boston
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You do want to be careful about pre-compressed air or CO2 unless the container is large enough that the internal pressure drop isn't that great when you do this blasting. I guess a scuba tank should be okay for a few bursts. Back when I used to do inspections, I can remember getting them real cold during discharge, but they'd just be sitting there discharging for several minutes, a lot longer than you'd be doing.
Fellows sells or used to sell an oil-less CO2 cartridge-based blower for computer keyboards. Sounds like a good idea for mirrors, right? WRONG! These cartridges are so small that it is very difficult to use them effectively without getting them very cold--cold enough to spit little dry ice chips on the mirror. You can get a separation between the coating and the substrate that way.
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Mike
- 7" f/6.7 home-built Newt and equatorial platform
- 120mm f/8.3 home-built grab-n-go Newt
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rboe
Reged: 03/16/02
Posts: 63466
Loc: Phx, AZ
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Using compress air to clean computers and keyboards - any dusty equipment in a shop, will aerosols the dust, then you breath it. Worse than smoking. Best to use a good quality vacuum.
It's a personel irk of mine when I see folks shoot all that crap into the air. Don't get me going on folks that eat over their computer!
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Ron
NS11GPS
Pronto
16" dob
127mm F9 Surplus Shed/Crawmach kit scope
Coronado SolarMax 40 on a Celestron 102 Wide Field
Best of ATM
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Anonymous
Unregistered
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I think if you used a good sized can, about the size of an oven cleaner can, and do shorts bursts, you might be able to get away with compressed air? The short bursts would keep it from getting too cold and keep it from spitting. And you need to keep the can level. I've noticed on computers when I tip the can, it tends to spit. But it just evaporates immediately. Oh well, I guess with careful practice it might work, I guess its just a risk youd have to take, or you could go the big co2 scuba tank route. Just my 2 cents. (I guess I cant talk until I've actually tried it when I get my scope)
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Anonymous
Unregistered
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Quote:
Mike, you ruined my plans! I was looking at getting a canned air product. I may have to go with plan B and get a scuba tank filled with CO2 (we use them to recharge our air pistols, get them filled at welding supply shops). Just need a regulator so 3000psi doesn't come out at strip the coating off on its' own accord!
Don't use CO2. No matter how big the container is, the rapid expansion of the gas escaping from the nozzle will create a large cooling effect. I would estimate that it would be enough to at least condense water out of the air and get it all over the mirror.
The only way to avoid this would be if the flow through the nozzle was very low (regulator set to a very low pressure). But then, it wouldn't do much in the way of blowing dust off.
Also, pure CO2 is somewhat corrosve, though the HCOOH (carbonic acid) that would form (from combining with condensed ambient moisture) will not attack aluminum.
I would go with dry nitrogen. Semiconductor grade would be best, though I'm not sure where you would get small quantities.
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rboe
Reged: 03/16/02
Posts: 63466
Loc: Phx, AZ
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Frankie;
Luckily we have very dry air! My neighbor has a CO2 tank already so I can test your theory for my area. Thanks for the heads up.
Since I'm just doing quick dust off (in my mind that's what I'm thinking anyway) I'm hoping it won't be an issue. We shall see. Cross your fingers.
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Ron
NS11GPS
Pronto
16" dob
127mm F9 Surplus Shed/Crawmach kit scope
Coronado SolarMax 40 on a Celestron 102 Wide Field
Best of ATM
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Anonymous
Unregistered
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I just remembered that PHX has its share of wafer fabs. So I figure there should be suppliers of semi-grade gasses. A lot of their business is, of course, filling and servicing the big LN2 tanks that many fabs draw from. But there should also be a market for N2 gas sold in cylinders. They can't be too expensive. We used to use a boatload of them each month where I used to work, mostly for small so-called "dry boxes" where wafers or other sensitive stuff were stored.
So if the CO2 doesn't work, try the N2 route.
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rboe
Reged: 03/16/02
Posts: 63466
Loc: Phx, AZ
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Go figure, a fab needs lots' of clean water. A desert would be your first choice too wouldn't it be?
I'll have to look into that, get some prices. See if it's not cheaper to have it recoated every other year.
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Ron
NS11GPS
Pronto
16" dob
127mm F9 Surplus Shed/Crawmach kit scope
Coronado SolarMax 40 on a Celestron 102 Wide Field
Best of ATM
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litespeed
scholastic sledgehammer
Reged: 10/31/03
Posts: 984
Loc: Space Coast, FL
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I find this thread interesting. Because I live at the beach. If I never cleaned my mirrors and or correctors....... I would never be able to see anything (with clarity). In one observing session from my backyard a noticeable amount of salt will cover the lens or mirror. After a month it really starts to affect the images. In one of the scopes it appears as if the mirror is actually corroding on the surface? Not sure if that is possible. Everything else corrodes and rusts out here so I assume it is normal.
My routine so far has been to pour distilled water over the optics and then blow dry with a squeezy bulb.
Does anyone have any good advice for optics that "do" need cleaning on a regular basis?
AJ
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AJ
5"MAK
TouCam
20D
Uh Oh!... Whats that noise?...
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Anonymous
Unregistered
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AJ,
If you do not get some good answers here, visit the Optical Shop section of this forum and ask Al M the same question and describe your circumstances. He is a specialist in optical coatings amoung other things.
I am also interested as I want to take my scope to the coast this summer.
Keith
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Stacy
Star Partyer
Reged: 09/15/02
Posts: 3321
Loc: 48.0153° N, 122.0625° W
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Quote:
My routine so far has been to pour distilled water over the optics and then blow dry with a squeezy bulb.
Hi AJ,
That is probably the most effective and gentlest way if you have to clean often. I would recommend not letting the salt remain for any length of time, as it is highly corrosive.
Regards,
Stacy
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Scott
super member
Reged: 01/14/04
Posts: 105
Loc: CT
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I have a side issue to the lens cleaning and that is trying to re-seat this five lb. plus lens and cell, into what was a very tight fitting, but no longer precisely round, 8" metal tube. I stood the tube on end on the floor...but after 10 min. of 'almosts', I gave up. I ended up sliding the mounting ring up to the end and tightening it up to force the shape...this worked, but not without a lot of effort. I must admit that I hope to never have to go through that again anytime soon. If anyone has a hint, I would love to hear it.
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Scott
TAK Mewlon 210
Intes MN-61
Vixen ED 102S
GM8
UA Maxistar
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Jim
scholastic sledgehammer
Reged: 02/09/04
Posts: 975
Loc: Cincinnati (UC Bearcats), Ohio
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What about cleaning mirror diagonals?
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Rammysherriff
Carpal Tunnel
Reged: 03/26/04
Posts: 1967
Loc: Lancs, UK.
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Just to revive something:
electrostatic cleaning! Has anyone considered using electrostatic methods of
a) removing dust from a mirror surface?
b) preventing further particles sticking to it by electrostatic devices?
c) does static electricity play any part in sucking particles onto the mirror, can it be avoided or prevented?
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Simon.
One man and his shed: http://s211.photobucket.com/albums/bb288/Astroshed/
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Norvin
Carpal Tunnel
Reged: 10/10/03
Posts: 1540
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Orion's Directions
Norvin
Post #497
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 Norvin
10" Black X Class (GSO) Dobsonian
Norvinian Dobsonian Telescope Mount
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