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In-Store Selection!
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| Meade?
Digital Electronic Series ?
Refracting and Reflecting Telescopes
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In-depth tips and
information. |
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A Word
about ?Power?
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When selecting a
telescope, one of the least important factors to
consider is the power, or magnification, of the
instrument. The key to observing fine detail, whether on
the surface of the Moon or on a license plate one mile
in the distance, is not power, but aperture.
Aperture
refers to the diameter of the telescope?s main
(objective) lens or primary mirror.
The power at which a
telescope is operating is determined by the eyepiece
employed. Within reason, power is useful, but the most
common mistake of the beginning observer is to
?overpower? the telescope and to use magnifications
which the telescope?s aperture and typical atmospheric
conditions can not reasonably support. The result is an
image which is fuzzy, ill-defined, and poorly resolved,
through no fault of the telescope. Keep in mind that a
smaller, lower-power, but brighter and well-resolved,
image is far superior to a large, high-power, but dim
and poorly-resolved, one. |
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How
to Calculate Power
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magnification, or power, at which a telescope is
operating is a function of the focal length of
the telescope?s main (objective) lens (or
primary mirror) and the focal length of the
eyepiece employed. The focal length of the
objective lens is the distance between the lens
and the point at which it brings light rays to a
focus; this focal length (in mm) is printed on a
label affixed to the optical tube of every Meade
telescope. The focal length of each eyepiece
(which typically ranges from 4mm to about 40mm)
is printed on the upper surface of the eyepiece.
To calculate power, divide the focal length of
the eyepiece into the focal length of the
objective lens:
[ Power =
focal length of objective lens / focal length of
eyepiece ]
Example: The Meade DS-80EC telescope has
an objective lens focal length of 900mm; when
this telescope is used with a 25mm eyepiece, a
power of 900 ?25 = 36 power (written as
?36X?) results.
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Choosing
Your Eyepieces
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on how much you plan to use your telescope, and
for what applications, you may wish to add 2 or
3 eyepieces and/or a multiplying ?Barlow?
lens to your on-hand eyepiece selection.
On any of Meade
Digital Electronic Series telescope models,
eyepieces of 25mm or 40mm focal length are best
suited for extended star fields or nebulosities
(such as the Orion Nebula, the Pleiades star
cluster, or the Andromeda galaxy), or for
terrestrial applications. These eyepieces result
in low-powers, wide fields, and bright images.
When viewing the Moon and planets, eyepieces
between 4mm (high power) and 18mm (moderate
power) are advised. The highest powers should be
employed only under favorable atmospheric
conditions.
The Meade #126 2x
Barlow Lens can be used with any DS-Series model
in conjunction with an eyepiece, and results in
a doubling of the power obtained when the
eyepiece is used alone. |
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