Celestron FirstScope 76mm f/4 Signature Series Moon Alt-Az Reflector Telescope User Manual
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While your 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 primary and secondary mirrors 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 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 downward 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 a return authorization number and price quote.
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The optical performance of most Newtonian reflecting telescopes can be optimized
by re-collimating (aligning) the telescope's optics, as needed. To collimate the
telescope simply means to bring its optical elements into balance. Poor collimation
will result in optical aberrations and distortions.
Your telescope should rarely need to be re-collimated unless it has been roughly
treated, dropped, etc.
Before collimating your telescope, take time to familiarize yourself with all its
components. The primary mirror is the large mirror at the back end of the telescope
tube and can only be adjusted at the factory. The secondary mirror (the small,
elliptical mirror under the focuser in the front of the tube) has three adjustment
screws (Phillips head) to perform collimation.
Figure 6-1
A collimated telescope
should appear as a
symmetrical ring pattern
similar to the diffraction
star disk seen here.