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How to Use Acetone to Clean a Telescope Mirror

If you've been using your telescope for any length of time or have left it uncovered in storage, the telescope's mirror has probably picked up some dirt or dust, clouding your view of the night sky. Telescope mirrors are sensitive optical surfaces that require a light touch when cleaning with acetone. Since even a tiny scratch can make the mirror un-usable, it's very important to handle the mirror gently and clean it slowly and methodically. Take your time and be gentle while following these instructions.

Things You'll Need

Acetone
Window cleaner such as Windex
Paper towels
Cleaning surface

Instructions

- 1
  Spread your materials out on your work surface. Acetone is a very strong solvent, so choose a non-reactive, non-finished surface such as a plastic mat or cutting board.
- 2
  Pull a single sheet of paper towel off the roll and cut it into four smaller squares, then fold these over to produce four double-sided pads.
- 3
  Dampen one of the pads with acetone. Pour a little acetone on the mirror and--working gently in a circular motion--rub the spots off your telescope mirror. Flip the pad over midway through. Acetone dries quickly, so stop rubbing just as the mirror begins to dry. Add more acetone to a new pad and buff again, gently, if necessary. Discard the used acetone pad.
- 4
  Spray a very thin film of glass cleaner onto the mirror. Barely moisten another pad in the same way. Working in gentle, circular motions, wipe the mirror until it dries. If stains remain on the surface, moisten the pad just a little more (do not re-wet the mirror) and wipe at the stain lightly in a circular motion. Repeat until the stain disappears.

Astronomy