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CALCULATING POWER
The power, or magnification, at which a telescope is operating is determined by two factors: the optical, or
focal length of the telescope’s main (objective) lens and the focal length of the eyepiece being used.
The focal length of the Telestar 40AZ-T’s objective lens is 600mm. To compute power, divide the focal length
of the eyepiece into the focal length of the objective lens. The resulting quotient is the magnifying power of
the telescope when used with the eyepiece in question. For example, the 25mm eyepiece yields with the
Telestar 40AZ-T, a power of:
Power = 600mm ÷ 25mm = 24X
Similarly, if the 6mm eyepiece is used:
Power = 600mm ÷ 6mm = 100X.
A few words about power. While the theoretical power or magnification of a telescope is virtually limitless,
there are, however, practical limits imposed by the Earth’s atmosphere as to what can be seen well at a
given power. The most useful higher magnification with any 40mm diameter telescope is in the range of 24
to 100 power.
The general rule regarding power: Only use as much magnification as supports a steady, well-defined
image. The stability of the air varies and is one reason why having various eyepieces is highly desirable.
Higher powers are no guaranty of better images; in fact, the opposite is often true. Also, keep in mind, that
land viewing and wide-field, deep-space observation are, generally, low power applications of your
telescope.
MAINTENANCE
The AZ-T telescope should be stored in a dry and dust-free place. It should not be stored in direct sunlight.
When not in use, keep the lens covered so that it stays clean. Avoid cleaning the lens. A little dust on the
the lens hardly affects image quality and should not be considered reason to clean the lens.
SPECIFICATIONS
Objective (main) lens focal length . . . . . . . . . . .600mm
Objective lens diameter . . . . . . . . . . . . . . . . . . .40mm, 2-element achromat
Viewfinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2x
Mounting type . . . . . . . . . . . . . . . . . . . . . . . . . . .Altazimuth
Eyepieces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25mm, 6mm
Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24X, 100X
