Celestron 31058 L E S C O P E M a I N T E N a N C E, Care and Cleaning of the Optics Collimation

T E L E S C O P E M A I N T E N A N C E

Care and Cleaning of the Optics

Collimation

After you have set up your telescope and started using it, there are a few things to remember for future reference.

To minimize the need to clean your telescope, replace all lens covers once you have finished using it. Since the front of the telescope tube is open ALWAYS replace the front cover when the telescope is not in use. This will minimize the amount of contaminants from entering the optical tube and minimize the number of times your telescope needs to be cleaned.

The long tube of your Newtonian telescope acts as a dew shield to prevent moisture from building up on the primary mirror. However, on extremely damp nights, the tube may only slow the formation of dew on the primary mirror. If dew condenses on the primary mirror it can be removed with a hair dryer or by pointing the tele- scope at the ground.

Occasionally, dust and/or moisture may build up on the primary mirror of your telescope. Special care should be taken when cleaning any optical instrument so as not to damage the optics. Internal adjustments and cleaning should be done only by the Celestron repair department. If your telescope is in need of internal cleaning, please call the Celestron repair department for specific information on service.

Exact mirror alignment (i.e., collimation) of a fast f-number Newtonian reflector is necessary in order to obtain the best optical image quality possible. Although your telescope was fully collimated at the factory, you should check collimation to ensure that rough handling has not altered the alignment of the mirrors.

To determine whether or not recollimation is necessary, the telescope should be set up outside at night. It should be a still night and one in which you have let the telescope sit outside for 30 to 45 minutes before attempting collimation. You should also wait for a night with good seeing conditions and avoid looking over anything that produces heat waves (i.e., roof tops, car hoods, etc.).

Pick a bright star and center it in the field of the telescope. Study the image of the star while racking it in and out of focus using 30 to 60 power for every inch of aperture. For your G-8N this equates to about 240 to 480 power and for the C150- HD is about 180 to 360 power.. If an unsymmetrical focus pattern is present, then it may be possible to correct this by recollimating only the primary mirror. Simply removing the ocular during the daytime and looking down the focus tube is NOT a satisfactory way of determining collimation. Read the procedural instructions through completely BEFORE attempting!

To star collimate, the telescope should be on either a motor driven (i.e., tracking) equatorial mount that is approximately polar aligned or pointed at a stationary star without the motor drive running. Polaris, the North Star, is the perfect collima- tion star for northern hemisphere observers since it appears motionless against the background sky long enough to perform the collimation procedure. Polaris is the last star in the handle of the Little Dipper (Ursa Minor) and its distance above the northern horizon is always equal to your latitude angle.

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