Celestron OMNI XLT 102 manual Care and Cleaning of the Optics, Collimation of Refractors

While your telescope requires little maintenance, there are a few things to remember that will ensure your telescope performs at its best. Each optical design type has special collimation instructions described below.

Care and Cleaning of the Optics

Occasionally dust and/or moisture may build up on the objective lens, the corrector plate, or primary mirror depending on which type of telescope you have. Special care should be taken when cleaning any instrument so as not to damage the optics.

If dust has built up on the optics, remove it with a brush (made of camel’s hair) or a can of pressurized air (spray at an angle to the glass surface for approximately two to four seconds). Then, use an optical cleaning solution and white tissue paper to remove any remaining debris. Apply the solution to the tissue and then apply the tissue paper to the optics. Low pressure strokes should go from the center of the lens (or mirror) to the outer portion. DO NOT

rub in circles!

You can use a commercially made lens cleaner or mix your own. A good cleaning solution is isopropyl alcohol mixed with distilled water. The solution should be 60% isopropyl alcohol and 40% distilled water. Or, liquid dish soap diluted with water (a couple of drops per one quart of water) can be used.

Occasionally, you may experience dew build-up on the optics of your telescope during an observing session. If you want to continue observing, the dew must be removed, either with a hair dryer (on low setting) or by pointing the telescope at the ground until the dew has evaporated.

If moisture condenses on the inside of the optics, remove the accessories from the telescope. Place the telescope in a dust-free environment and point it down. This will remove the moisture from the telescope tube.

To minimize the need to clean your telescope, replace all lens covers once you have finished using it. Since the cells are NOT sealed, the covers should be placed over the openings when not in use. This will prevent contaminants from entering the optical tube.

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 factory for information.

Collimation of Refractors

Be sure to completely read carefully before attempting collimation. Collimation is the process of aligning the optical axis of each optical element with each other and with the mechanical axis of the telescope tube. For a refractor telescope design this means aligning the optical axis of the objective lens with the optical axis of the eyepiece on the other end of the tube. Your Omni refractor was properly aligned at the factory. However, extremely rough handling while traveling may eventually alter the alignment of the lens. Your Omni refractor telescope may come with an adjustable objective lens housing to assist in the alignment of the optical axis. It is rare that collimation would be necessary and if your telescope does not have collimation adjustment screws, you may have to send it to the factory for alignment.

To determine whether or not re-collimation 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 15 to 30 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.).

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Collimation	Mounting Screws
Screws	(Phillips head)
(Allen head)

Figure 7-1

Objective lens housing (with lens shade removed)

show mounting and collimation screws.