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While your NexStar telescope requires little maintenance, there are a few things to remember that will ensure your
telescope performs at its best.
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Occasionally, dust and/or moisture may build up on the corrector plate of your telescope. Special care should be
taken when cleaning any instrument so as not to damage the optics.
If dust has built up on the corrector plate, remove it with a brush (made of camel’s hair) or a can of pressurized air.
Spray at an angle to the lens 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
lens. Low pressure strokes should go from the center of the corrector 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 corrector plate 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 corrector, remove the accessories from the rear cell of 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 rear
cell is NOT sealed, the cover should be placed over the opening 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 a return authorization number and price quote.
Collimation
The optical performance of your NexStar telescope is directly
related to its collimation, that is the alignment of its optical
system. Your NexStar was collimated at the factory after it
was completely assembled. However, if the telescope is
dropped or jarred severely during transport, it may have to be
collimated. The only optical element that may need to be
adjusted, or is possible, is the tilt of the secondary mirror.
To check the collimation of your telescope you will need a light
source. A bright star near the zenith is ideal since there is a
minimal amount of atmospheric distortion. Make sure that
tracking is on so that you won’t have to manually track the star.
Or, if you do not want to power up your telescope, you can use
Polaris. Its position relative to the celestial pole means that it
moves very little thus eliminating the need to manually track it.
Before you begin the collimation process, be sure that your
telescope is in thermal equilibrium with the surroundings.
Allow 45 minutes for the telescope to reach equilibrium if you
move it between large temperature extremes.
Collimation
Screws
Corrector
Plate
Figure 7-1
The three collimation screws are located on the
secondary mirror holder in the center of the
corrector plate.