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How do I Remove a Dobsonian Mirror?

Dobsonian telescopes are among the most powerful large-aperture---with a wide opening in the front---telescopes available for amateur astronomers. These telescopes consist of a long, hollow tube with an open hole in the front that is aimed toward the night sky, and at the bottom end is a large mirror, called the primary mirror. Because the tube is open on one end, the primary mirror is prone to dust collecting on its surface and must be removed for cleaning.

Things You'll Need

Screwdriver set

Instructions

- 1
  Look at the back of your Dobsonian telescope and identify the round plastic, or aluminum, primary mirror holding cell. This cell is a containment system that holds the mirror. This cell is at the opposite end of the telescope from where the open end is located, or at the far opposite end from the end on which the lens is located.
- 2
  Identify the mirror adjustment screws and the cell mounting screws. The adjustment screws are typically three in number, in a triangular-shaped configuration. These screws are always located within the innermost part of the circular mirror cell edges. Avoid loosening these screws, as this will require a complete realignment of the telescope mirror and may be a very time-consuming process.
- 3
  Loosen all of the mirror cell mounting screws located around the outer edge of the mirror cell, using a screwdriver. Loosen each one only about two turns.
- 4
  Grasp the entire mirror cell with the hand that isn't being used to operate the screwdriver and gently press the cell against the telescope tube so it won't fall off when removing the screws. Remove each of the mounting screws and lay them off to the side in a location where they won't become lost.
- 5
  Lay the screwdriver down while holding the mirror cell against the telescope tube and hold the mirror cell with both hands. Slowly pull the cell straight and away from the main telescope body. Hold the entire cell so the reflective surface of the mirror is facing skyward, not with the mirror pointing downward to the ground. Set the mirror down gently without jarring it to prevent misalignment or damage to the mirror or the adjustment mechanism.

Astronomy