cosmic camper
member
Reged: 06/12/08
Posts: 21
Loc: Santa Cruz, CA
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I've been using a soft brush for years to lightly dust particles off my mirrors. But sometimes that can result in tiny sleeks. I never tried compressed air, because I read you shouldn't use the ones with propellents (like those used for computers). So what type of compressed air can you use and where can you buy it?
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Paul,
the Cosmic Camper
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2005 Ford Econoline camper van
16" Astro Sky/Swayze truss tube dob
DGM 5.5" off-axis dob
Celestron Nexstar 5SE
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Fiske
Carpal Tunnel
Reged: 03/14/04
Posts: 1935
Loc: Missouri / United States
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Paul:
I would avoid any sort of canned, compressed air. They all utilize propellents that can deposit stuff on your optics. There is a UTube video (link in this thread ) which presents an excellent (and simple) approach to cleaning telescope mirrors.
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Fiske Miles
Nikon 8x42 LX / 12x50 SE Binos
Mini Borg 60ED, TV-101, AT80Ach, XT-8, C11/CI-700, 22-Inch Dob
Way too many Nagler eyepieces
http://www.fiskemiles.blogspot.com/
www.fiskemiles.com
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cosmic camper
member
Reged: 06/12/08
Posts: 21
Loc: Santa Cruz, CA
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Thanks, Fiske. Good video. Exactly what I do once or twice a year.
But I'm asking for in between cleanings, when you see several dark specs on there that you want to get off. A brush works okay. But I've heard other people say they use compressed air. Maybe they meant from an air compressor. Does anyone know if all the canned air products have these harmful propellents?
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Paul,
the Cosmic Camper
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2005 Ford Econoline camper van
16" Astro Sky/Swayze truss tube dob
DGM 5.5" off-axis dob
Celestron Nexstar 5SE
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Wes James
Carpal Tunnel
Reged: 04/12/06
Posts: 2320
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Paul-
Even with an air compressor, you have to be careful- as when you compress air- you heat it- which generates moisture, so if your air compressor doesn't use a water trap, you wouldn't want to use that anyway. Also you want to make sure that the compressor won't have any oil vapor in it, or you'd be worse off than you were to begin with. Don't know is all canned airs are problematic- they all have to have propellants, and that is the source of the problems. The bulb like they make for camera cleaning- with the brush on the end is one clean source of air... if you want more pressure, you could take a turkey baster- make a reducer for the end of it so you're blowing air out of a smaller diameter tube opening- say, 1/16" as opposed to the 1/4" opening of the typical baster... that should give you enough air pressure to blow any dust off- with no danger of contaminants/propellants.
Hope you're o.k. from all the fires out there???
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Wes
Atlantic Beach, FL
Some bino’s from Miyauchi 5x32 Binon's up through Garrett 20x110 Signature's,
Some telescopes from a Stellarvue 80mm NHNG up through a couple of 8” reflectors…
And a wonderful 4.25" Delmarva Shiefspiegler!
Some good friends, made here on C/N.
Oh- several cats and a wonderful wife!
Anyone want a cat???? :-O
"When your work speaks for itself- Don't Interrupt" -Gamble Rogers
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Fiske
Carpal Tunnel
Reged: 03/14/04
Posts: 1935
Loc: Missouri / United States
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Paul:
I agree with Wes that you want to be careful with air compressors.  OTOH, I own a portable contractor style compressor, one of the dual tank models, and also got an airline filter for it. I experimented with blowing air against a piece of plate glass until I was satisfied that no moisture, oil, or other residue is emitted. I routinely use it on optics, even for drying mirrors after washing them. I don't know how this would compare with a cheapie type compressor. I'm using an Emglo that cost a little under $400, if memory serves.
I also use it in my shop to run airnailers and the like. I have always been very careful with the hose, which is stored inside. I have also never used an inline oiler, needless to say...
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Fiske Miles
Nikon 8x42 LX / 12x50 SE Binos
Mini Borg 60ED, TV-101, AT80Ach, XT-8, C11/CI-700, 22-Inch Dob
Way too many Nagler eyepieces
http://www.fiskemiles.blogspot.com/
www.fiskemiles.com
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Achernar
Post Laureate
Reged: 02/25/06
Posts: 3478
Loc: Alabama, USA
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None is the kind you should use, because compressed air often has oil, water or both in it. If you've ever seen the sort of junk that can come out of an air compressor, you would never use compressed air on your mirrors. The blast of air can turn any grit on the mirror into what amounts to sandblasting which is not a good thing for optical surfaces.
Taras
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10-inch F/4.5 Discovery Dob
6-inch F/8 Homebuilt Dob
4 1/4-inch F/4 Homebuilt reflector
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jcjr
professor emeritus
Reged: 01/06/08
Posts: 563
Loc: TN, USA
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I have no opinion re advisability of compressed air for this purpose. Re sand-blasting a mirror, one could reduce the pressure for a first pass, to take off the light grit before cranking it up...
Knowing very little of air compressors, I have a medium-sized 'Husky' home depot oil-less pancake compressor that's been working fine for small air tools and blowing stuff off. The main issue is that it is very loud.
With an air cleaner on it, the output seems pretty dry and oil-free.
Then I got a Harbor Freight small oil-using dual-tank compressor for a friend's Christmas present. Similar to the small Dewalt dual-tank jobbies, costed less than my Husky. A little over $100.
The immediately noticeable difference with the oiled compressor is that it is very quiet. It doesn't get on your nerves when it switches on. The oiled compressor chugs along slow-steady and quiet, getting the job done. Wheras the oil-less compressor sounds like a hot-rod winding out with the pedal-floored.
Assuming air cleaners work as advertised, wish I'd got an oiled compressor rather than the oilless model. Just watching the oiled model pumping slow steady and quiet, I'm betting my friend's oiled compressor will last longer than my airless too. Seems to be running much farther below the 'red line'.
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CPC 1100, C102SLT, SV F80, Meade 70 & 60 AZT
Q70 38mm, Pan24, Meade 5K 18mm UW, Axiom LX 15mm, Nagler 13T6, Axiom LX 10mm, Expanse 20mm, 9mm, 6mm, BO/TMB 5mm, 2.5mm
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Luigi
Carpal Tunnel
Reged: 07/03/07
Posts: 1591
Loc: Massachusetts
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I use canned air all the time on optics at work. It's not really air. The gas that comes out is the propellant. The only issue I found is if you shake the can while spraying, or don't keep it upright, it can spray liquid, which immediately vaporizes but can leave behind a residue. I also used air from an oilless compressor.
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17.5" f/5 Discovery Truss
IM715 7" f/15 MCT (due July!)
Eon-120ED refractor
CG5A coffee grinder, Orion Skyview Alt-AZ
35,19,15 Pans.9 Nag. Meade 24.5 4kSWA, 4.7 5kUWA.
BO-TMB 7mm planetary.
Zeiss Diascope 85
Zeiss, Leica, Canon IS, Fujinon, Nikon binos
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Fiske
Carpal Tunnel
Reged: 03/14/04
Posts: 1935
Loc: Missouri / United States
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Luigi:
Extreme sport?
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Fiske Miles
Nikon 8x42 LX / 12x50 SE Binos
Mini Borg 60ED, TV-101, AT80Ach, XT-8, C11/CI-700, 22-Inch Dob
Way too many Nagler eyepieces
http://www.fiskemiles.blogspot.com/
www.fiskemiles.com
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Mozhoven
professor emeritus
Reged: 05/26/05
Posts: 727
Loc: Middletown, CT
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I haven't tried it yet, but I suspect the oil-less air compressors used for airbrushes would be ideal.
A) They only put out about 30psi
B) No oil contamination/vapor (oil-less motor)
C) Very quiet
D) Reasonably priced. (~$100)
E) Very, very compact. Fits in a shoebox (or large eyepiece case)
As long as you install a good water filter there should be no issues at all that I can see. Airbrushes are notoriously sensitive to anything foreign in the air supply, I know mine is. With my airbrush costing $200 the air compressor must be perfect.
Anyway, I'll fire it up sometime and try it out on a piece of glass. I'll let you know.
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Jeremy Davis
Orion XT12i - 12" f/4.9 "Alfred E. Newtonian"
Wyorock Custom Crayford
13mm Ethos The "Freshmaker"
12x60 Oberwerk Binos
www.jdavisgallery.com
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cosmic camper
member
Reged: 06/12/08
Posts: 21
Loc: Santa Cruz, CA
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After hearing all this, I think I'll stick with my camera bulb and brush. Maybe I'd go all out and try Wes's turkey baster idea. This seems like a case of the cure being worse than the illness. 
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Paul,
the Cosmic Camper
__________________________________
2005 Ford Econoline camper van
16" Astro Sky/Swayze truss tube dob
DGM 5.5" off-axis dob
Celestron Nexstar 5SE
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Fiske
Carpal Tunnel
Reged: 03/14/04
Posts: 1935
Loc: Missouri / United States
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Paul:
My advice would be not to try removing specs between cleanings. I don't like the idea of anything touching the mirror surface, and a few specs simply won't have any impact on what you see in the eyepiece. The potential for damaging the mirror when trying to brush specs off FAR outweighs any potential benefit in my opinion.
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Fiske Miles
Nikon 8x42 LX / 12x50 SE Binos
Mini Borg 60ED, TV-101, AT80Ach, XT-8, C11/CI-700, 22-Inch Dob
Way too many Nagler eyepieces
http://www.fiskemiles.blogspot.com/
www.fiskemiles.com
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David E
Pooh-Bah
Reged: 05/25/06
Posts: 1471
Loc: North Carolina
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Quote:
I've been using a soft brush for years to lightly dust particles off my mirrors. But sometimes that can result in tiny sleeks. I never tried compressed air, because I read you shouldn't use the ones with propellents (like those used for computers). So what type of compressed air can you use and where can you buy it?
I never use canned or compressed air. Every astronomer should have a Giotto's Rocket Air.
David E
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So when at times the mob is swayed
To carry praise or blame too far,
We may choose something like a star
To stay our minds on and be staid.
-Robert Frost
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Fiske
Carpal Tunnel
Reged: 03/14/04
Posts: 1935
Loc: Missouri / United States
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David:
This seems like a cool product. Thanks for posting it to this thread.
Here is a question. I have heard many people say things like NEVER use an air compressor to blow dust, moisture, whatever, off you mirror because it can deposit oily residue, moisture, whatever on your mirror. BUT, I have yet to hear from anyone who actually had that happen and we have already had a number of people on this thread, myself included, who use compressors regularly with no ill effect.
If you have used an air compressor on your mirror, and it caused a problem by depositing stuff on the mirror, please speak up! 
I'm not interested in tales of what people may have seen come out of air compressors. It wouldn't surprise me in the least to hear about oil blown out of an air compressor that includes an inline oiler (contractors use these to keep their air tools oiled and operating well). No, I want to hear from amateur astronomers who have actually blown stuff on their mirror with an air compressor. Not a can of compressed air -- a compressor.
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Fiske Miles
Nikon 8x42 LX / 12x50 SE Binos
Mini Borg 60ED, TV-101, AT80Ach, XT-8, C11/CI-700, 22-Inch Dob
Way too many Nagler eyepieces
http://www.fiskemiles.blogspot.com/
www.fiskemiles.com
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davidpitre
Pooh-Bah
Reged: 05/10/05
Posts: 1363
Loc: Central Texas
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I've used an compressor for years on lens objectives, corrector plates ,mirrors, and eyepieces without issue.
I do regularly drain my compressor of water in the bottom though. Amazingly, many people with air compressors are not aware of the water that accumulates in them.
My eyepieces are more commonly blown clean with the Giotto rocket, ' Great product.
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David
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Mozhoven
professor emeritus
Reged: 05/26/05
Posts: 727
Loc: Middletown, CT
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While I am an advocate for using air compressors, I do want to include a caveat. If the compressor is old and/or been abused it can pass oil through the line. I recently purchased a compressor that had been run for long durations without enough oil. It blew out oil like crazy. I replaced the pump and it now runs clean.
But, as I posted earlier, I think the oil-less air compressor for airbrushes is ideal.
This is the one I have: Harbor Freight - 1/8 HP Oil-less Airbrush Compressor $59.99
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Jeremy Davis
Orion XT12i - 12" f/4.9 "Alfred E. Newtonian"
Wyorock Custom Crayford
13mm Ethos The "Freshmaker"
12x60 Oberwerk Binos
www.jdavisgallery.com
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Fiske
Carpal Tunnel
Reged: 03/14/04
Posts: 1935
Loc: Missouri / United States
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Jeremy:
Thanks for posting the link to the Harbor Freight compressor. Compressors designed to run air tools like the EmGlo I own are really overkill for blowing off optics. The HF model is much less expensive and a much better choice for this use.
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Fiske Miles
Nikon 8x42 LX / 12x50 SE Binos
Mini Borg 60ED, TV-101, AT80Ach, XT-8, C11/CI-700, 22-Inch Dob
Way too many Nagler eyepieces
http://www.fiskemiles.blogspot.com/
www.fiskemiles.com
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cosmic camper
member
Reged: 06/12/08
Posts: 21
Loc: Santa Cruz, CA
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The Giotto rocket - no AC required. I like it.
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Paul,
the Cosmic Camper
__________________________________
2005 Ford Econoline camper van
16" Astro Sky/Swayze truss tube dob
DGM 5.5" off-axis dob
Celestron Nexstar 5SE
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colinsk
scholastic sledgehammer
Reged: 01/17/08
Posts: 899
Loc: CA
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Cooling the compressed air in-line helps as well.
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Mahalo.
Coulter 10.1" Dobsonian
Coronado PST
TV-76
Lunt LS60TDS50FTBF1200- On Order 
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Joe Cipriano
Entropy Personified
Reged: 09/03/05
Posts: 3818
Loc: Uh... anyone have a GPS?
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Question: Are the small medical compressors used for nebulizers any different from the airbrush compressors? I'd think that anything intended for inhalation would be well-filtered and oil free.
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In the Land of Eternal Light Pollution & Great Pizza (Chicago)
SN-6, ED80, WO 66SD
Meade 208xt, SBIG ST-4
D70 (modified)
CGE (way modified)
A Wife who understands (unmodified)
Some other stuff...
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