Out of collimation | Collimated |
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Figure 12. A star test will determine if a telescope’s optics are properly collimated. An unfocused view of a bright star through the eyepiece should appear as illustrated on right if the optics are perfectly collimated. If the circle is unsymmetrical, as in the illustration on left, the telescope needs collimation.
To clean the primary mirror, carefully remove the mirror cell from the telescope. To do this, you must loosen the three screws from the end of the optical tube that are flush with the end of the tube. Completely loosen all three of the flush screws (do not loosen the other three screws) until the mirror cell comes out of the telescope.
Now, remove the mirror from the mirror cell by removing the three mirror clips that secure the mirror in its cell. Use a Phillips head screwdriver to unthread the mirror clip anchor screws. Next, hold the mirror by its edge, and remove it from the mirror cell. Be careful not to touch the aluminized surface of the mirror with your fingers. Set the mirror on a clean, soft towel. Fill a clean sink, free of abrasive cleanser, with room- temperature water, a few drops of liquid dishwashing deter- gent, and if possible, a capful of rubbing alcohol. Submerge the mirror (aluminized face up) in the water and let it soak for several minutes (or hours if it is a very dirty mirror). Wipe the mirror underwater with clean cotton balls, using extremely light pressure and stroking in straight lines across the surface. Use one ball for each wipe across the mirror. Then rinse the mirror under a stream of lukewarm water. Any particles on the surface can be swabbed gently with a series of clean cotton balls, each used just one time. Dry the mirror in a stream of air (a “blower bulb” works great), or remove any stray drops of water with the corner of a paper towel. Water will run off a clean surface. Dry the bottom and the edges with a towel (not the mirror surface!). Cover the mirror surface with Kleenex, and leave the entire assembly in a warm area until it is com- pletely dry before reassembling the telescope.
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