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Cleaning telescope optics can be important but there are some cautions that must be observed:

  • Only clean optics if absolutely necessary.  Do not clean optics more often than needed.

  • Be very careful not to scratch the optics.  Dusty glass is better than scratched glass.

  • Use only the recommended materials for cleaning.  Using other cleaning supplies may damage the optics.

Follow the instruction below and everything should be fine.  If you have any questions, feel free to contact us before proceeding and we will be happy to walk you through the process.

 

Cleaning Eyepieces

Eyepieces are the optical components that will need to be cleaned most often.  They are exposed to skin oils, gooey fingers ("Is this where I look?"), mascara, and a host of other optical traumas.  Fortunately, they are also the easiest parts to clean.

What to Use

  • Compressed air can

  • 100% cotton balls (not synthetic "cosmetic puffs")

  • Isopropyl alcohol

  • LensPen® or similar cleaning tool

How to Do It

For eyepieces that are not too dirty, a LensPen works great.  The LensPen has a brush on one end to clean off dust.  Once the dust is removed, the cleaning pad on the opposite end of the pen will remove smudges and fingerprints.

If a more thorough cleaning job is required, begin by blowing off any dust with a can of compressed air or use a soft brush.  It is important to clean dust off first, so that rubbing the glass does not scratch the coatings.  Apply a little alcohol to a 100% cotton ball.  Do not soak the ball, just get it damp.  Run the ball once around the area of the top lens of the eyepiece.  Then, use a second, dry cotton ball to dry the lens.  You may have to repeat this sequence several times using new cotton balls each time.  Any remnant fuzzies from the cotton balls can be blown off with the air can or brushed off.

 

Cleaning an SCT Corrector Lens

Cleaning the front corrector on an SCT is much more involved than cleaning eyepieces, and care should be exercised at all times.  Cleaning the corrector should be done as infrequently as possible.  Some dust on the lens will have no effect on the views through the telescope.  Once a year or less often is all that should be necessary unless something traumatic happens like a bird flying over and bombing your telescope.

Note:  Distilled water is safe to use on any optical surface.  Manufacturers will recommend using a mixture of water and isopropyl alcohol, but newer optical coatings may be stained by the alcohol.  Please contact us for specific recommendations if you are unsure of the best procedure for cleaning your telescope.

What to Use

  • Compressed air can

  • Distilled water (about a liter)

  • Spray bottle

  • 100% cotton balls

How to Do It

1)  Begin by pointing the nose of the telescope down at about a 45° angle.  This will allow the cleaning solution to run off the lens and not into the telescope.  Place a bucket or wastebasket under the corrector lens to catch the liquid that runs off.

2)  Use the compressed air can to blow of as much dust as possible.  Normally there will still be quite a bit of dust remaining that the air cannot remove.  This is fine.

3)  Put the distilled water into the spray bottle.

4)  Thoroughly spray the distilled water onto the corrector plate.  Use a pretty liberal amount.  This will carry much of the dust off the lens.

5)  Take a 100% cotton ball and roll it once across the lens.  This will pick up remaining dust rather than pushing it across the lens and scratching the coatings.  One cotton ball will only cover a few inches of the lens.  Throw the ball away and get a new one.  You will go through a lot of cotton balls, but they are a small price to pay to keep the optics in top shape.  Begin at the outside of the corrector and work your way around and in toward the center.

6)  Spray down the corrector again with the distilled water.

7)  This time, it is okay to wipe the cotton balls across the surface of the lens.  Wipe about 4-6 inches then get a new cotton ball.  Again, start outside and work in, continuing until the whole lens is dry.

8)  Leave the telescope pointed down to dry for about half an hour.  This will let the water that has leaked into the gasket behind the corrector lens evaporate.

9)  Once dry, blow off any remaining fuzzies from the cotton balls with the compressed air can.

 

Cleaning a Mirror

To clean a mirror, it normally must be removed from the telescope.  This will require collimating the system when it is reassembled.  See the Collimation page for details on doing this.  Cleaning a mirror should be done as infrequently as possible to prevent damage to the coatings.  A dusty mirror will not affect the view and is preferable to a damaged one.  Once a year or less often should be sufficient.  Use caution at all times while the mirror is out of the scope.

What to Use

  • Compressed air can

  • Distilled water (about a gallon)

  • 100% cotton balls

How to Do It

1)  Begin by removing the mirror cell from the telescope, then remove the mirror from its cell.  Place the mirror into an empty sink.

2)  Blow off any loose dust with the compressed air.  There will typically be some dust that will not come off.  This is fine.

3)  Tip the mirror up at about a 45° angle.  Slowly pour distilled water across the surface of the mirror to carry away more dust.

4)  Lay the mirror down flat and pour a small amount of water onto the surface.  The water should pool toward the center of the concave surface.

5)  Take a 100% cotton ball and roll it once across the mirror.  This will pick up remaining dust rather than pushing it across the mirror and scratching the coatings.  One cotton ball will only cover a few inches of the mirror.  Throw the ball away and get a new one.  You will go through a lot of cotton balls, but they are a small price to pay to keep the optics in top shape.  Begin at the outside of the mirror and work your way around and in toward the center.

6)  Wet the mirror again.

7)  This time, it is okay to wipe the cotton balls across the surface of the mirror.  Wipe about 4-6 inches then get a new cotton ball.  Again, start outside and work in, continuing until the whole mirror is dry.

8)  Leave the mirror to dry for a few minutes

9)  Once dry, blow off any remaining fuzzies from the cotton balls with the compressed air can.

Using a Telescope



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