Cleaning the Mirror of your Telescope

Cleaning the optics of any Telescope is an extremely delicate operation, and extreme care must be exercised at ALL times when doing so.

Telescope optics should be cleaned not more than once a year, unless absolutely necessary, as the coatings applied to optical surfaces are extremely thin, and can be very easily damaged.

NOTE: Never attempt to wipe a dry mirror with a lens tissue or dry Kleenex as it will scratch the coated surface.

NEEDED:

  • A large roll of soft absorbent cotton, not cotton balls - available at any chemist or drug store
  • Dishwashing detergent.
  • Tap water
  • Two litres of distilled or "clean" water

    TO CLEAN:

    1. CAREFULLY remove mirror from telescope, ensuring that you don't touch the surface of the mirror with anything.
    2. Flood mirror under a gentle stream of lukewarm water, to remove loose dirt and dust.
    3. Place a few drops of detergent on the wet surface, and gently swirl a large ball of wet cotton, fresh from the roll, over the mirror to remove all impurities.
    4. Rinse with tap water
    5. Give a final rinse with distilled or "clean" water
    6. Stand mirror vertically, and gently blot dry with large pieces of dry, CLEAN cotton. Take care not to touch the cotton with your fingers where it contacts the mirror to avoid picking up grease and oil form your skin. Continue to gently blot dry, replacing the cotton as it becomes wet, until all moisture is removed - DO NOT ALLOW TO AIR DRY.
    If these steps are followed and your mirror is kept clean, it should give you years of service before it needs re-coating.

    Adapted from information sheet by Morvac Optical Coatings.