Keeping Telescope Optics Clean

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Cleaning Procedures for Telescope Mirrors

In ACATW@egroups.com, Ellen wrote:

Hi all,

Can someone with Dob experience please give me some advice? I have some floating gunk on the big mirror of my 8" Dobsonian telescope. 

Dear Ellen:

"Floating gunk"?!!  Just what do you mean by floating gunk? 

If you just have some dust on your mirror you can used compressed air to blow it off. You could leave the mirror in the tube and set the tube so that the open end points downward (it doesn't have to be straight up & down). Blow the mirror off but don't hold the nozzle close to the mirror, stay about 1 foot away. Leave the telescope tube pointing downward for 15 minutes or so to let whatever dust & dirt you stirred up drift out of the tube.

A few words of caution: 

1. Don't try and blow it off like crazy. If it doesn't come off easily then leave it be. 

2. If you're using an air tank that you pumped up at the gas station and they don't have a good moisture separator in their air line, you could have some moisture in your tank. When spraying from your tank you could get water droplets all over your mirror.( If you are using a small throw-away can like you can get for blowing off electrical components I think you will be okay.) 

Please remember that when looking down your scope's tube in the daylight it may look pretty good. Look down it that night with a red flashlight and you may see all kinds of stuff! (There's just something about shining a red light down your scope when your eyes are dark adapted!) If your mirror needs to be cleaned then by all means clean it but, don't clean it too often! I usually have to clean mine about every 12 months,  but it all depends on how dirty it gets. I have been known not to clean it for almost 2 years. (I even had a dead moth laying on my mirror cell for about 6 months one time.) 

If you need to clean your mirror, did the manufacturer send you instructions on how to do it? One thing I recommend, no matter how you do it, is to use distilled water at least for the final rinse. 

Cleaning your optics too often will damage them. Here are a few tips to keep them clean: 

1. Always keep your eyepiece dustcaps on them when not in use. 

2. Always blow lightly into your dustcaps before installing them to remove any dust or dirt that can get onto your eyepiece. 

3. Use a 35mm plastic film cannister with the top on it to plug the hole of your focuser when the scope is not in use. 

4. For those of us with 10-inch and smaller telescopes: Spend a couple of dollars and get 2 plastic shower caps. When storing your scope, cover BOTH ends of the tube. (Watch out guys, some of them are pretty feminine looking!) 

5. When storing your telescope, lay it horizontally. Don't stick it out of the way somewhere with the tube pointing up & down - the dust in your tube will settle onto your mirror. 

PTE Steve:  Steven "Saratoga Smitty" Smith 
ACATW@eGroups.com

Cleaning Procedures for Telescope Mirrors

Download our PDF file: 
Cleaning Procedures for Telescope Mirrors

The following procedures for cleaning Newtonian telescope mirrors are recommended by QSP Optical Technologies

The following are two procedures for cleaning your coated optics. The following procedure has been used in many coating labs for surface treatment of metal optics as well as the final cleaning of aluminized optics.

FULL APERTURE CLEANING

Introduction: One person can easily clean their secondary mirror using this procedure. On larger optics one person may still be able to complete the procedure. However a second person could be helpful in tipping the mirror. The key to this procedure is to never let the coated surface dry until the final step is completed. Though this procedure may seem intimidating, with practice it will become easier and should help in providing the best imaging and longevity to your mirror. CLEAR SKIES!!

Materials: 

• 1-2 gallons of De-Ionized or Distilled H20, Sodium Lauryl Sulfate Soap (Joy, Palmolive, or ORVUS - found at veterinary supply stores)
• High pressure duster (available at an office supply store) of preferably High Pressure Dry Nitrogen
• 1-2 quarts Fresh Acetone or 2 Propanol (Alcohol) available at local chemical supply (i.e. VWR, J.T. Baker, Fisher)
• cotton or multi-lith pads, lens tissue (preferably) or facial tissue
• 4 quart pan or equivalent

Procedure:

1. Mix 1 teaspoon soap and two quarts of Distilled H20 in pan.
2. Placing the mirror on a flat surface slightly elevate one side and blow off any dust or dirt which has accumulated on the surface.
3. Repeat the procedure with Distilled H20 to minimize any contaminant which may scratch the surface during the contact cleaning.
4. Leaving the mirror on a flat surface immediately begin to gently wash the mirror surface with soap solution and cotton pad never letting the H20 dry on the surface. Should the H20 or soap solution dry on the surface a stain may result. If so repeat the entire procedure gently rubbing the stained area as well as the entire surface.
5. Leaving the mirror on the flat surface rinse the mirror with the remaining H20 to remove all the soap solution.
6. Leaving the mirror on the flat surface rinse the mirror with the acetone or alcohol until the H20 has been flushed from the surface.
7. Slightly elevating the mirror and using a back and forth motion blow the solvent off the mirror until dry.
8. Check the mirror for stains. If so repeat steps 3 through 7.
9. Dry the edges with tissue before lifting to avoid any streaks from remaining H20 etc.

LIMITED APERTURE CLEANING

Introduction: This procedure is for spot cleaning a mirror insitu due to moisture staining or other contamination. 

Materials:

• Lens or facial tissue
• 1 quart Fresh Acetone or 2 Propanol

Procedure:

1. Double fold tissue so you form a pad and when wet with solvent will not break.
2. Huff (breathe) on the area where the stain lies and wipe in one direction to remove the contamination.
3. Slightly dampen a second tissue with solvent and lightly wipe the area to remove the streak left by the first wipe,
4. Repeat step 3 until there is no visible streak left.
5. To check the cleaned area huff on the component again. As the vapor releases from the surface with inspection you will be able to detect whether the surface is still streaked or is now clean.

QSP Optical Technology, Inc. 1712-F Newport Circle, Santa Ana, CA 92705-5118 usa

Tel: 714-557-2299 Fax: 714-557-2170 Homepage: www.qsptech.com Email: infogqsptech.com