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How to Aluminize Telescope Mirrors

Applying aluminum to the surface is the last step in mirror building before installing the mirror inside the telescope. The aluminum is applied using evaporation. The mirror is placed in a vacuum chamber and aluminum is vaporized using electrical currents. The mirror needs to be cleaned to avoid having the aluminum coating chip or become uneven.

Things You'll Need

Vacuum chamber with operator's manual
Tungsten filament
99.99 percent or Grade A-1 aluminum
Paint thinner
Lint-free cloth
Ethanol
Pan
Hydrochloric acid
Distilled water
Silver (optional)

Instructions

- 1
  Use a lint-free cloth to clean the surface of the mirror with paint thinner.
- 2
  Wipe the mirror with semiconductor grade ethanol using a lint-free cloth.
- 3
  Dip the mirror for 10 minutes in a pan with one part hydrochloric acid in 10 parts distilled water.
- 4
  Install the tungsten filament in the vacuum chamber and add the aluminum strip on top of the filament.
- 5
  Install the mirror into the mirror holder inside the vacuum chamber.
- 6
  Seal the vacuum chamber and turn the vacuum pumps on. Wait until the pressure is 0.00001 mm of mercury.
- 7
  Turn the mirror rotators and evaporator on.
- 8
  Wait for the cycle to complete.

Astronomy