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In mapping the surface of the Earth, lines
of longitude are drawn between the North
and South Poles and lines of latitude are
drawn in an East-West direction, parallel
to the Earth's equator. Similarly, imaginary
lines have been drawn to form a latitude
and longitude on the celestial sphere.
These lines are known as
RRiigghhtt AAsscceennssiioonn
and
DDeecclliinnaattiioonn..
The celestial map also contains two poles
and an equator just like a map of the Earth.
The celestial poles are defined as those two
points where the Earth's North and South
poles, if extended to infinity, would cross the
celestial sphere. Thus, the North Celestial
Pole is that point in the sky where the North
Pole crosses the celestial sphere. The North
Star, Polaris, is located very near the North
Celestial Pole.
So just as an object's position on the Earth's
surface can be located by its latitude and
longitude, celestial objects may also be
located using Right Ascension and
Declination. For example: You can locate
Los Angeles, California, by its latitude
(+34
°) and longitude (118°). Similarly, you
can locate the Ring Nebula (also known as
"M57") by its Right Ascension (18hr) and
its Declination (+33
°).
•• RRIIGGHHTT AASSCCEENNSSIIOONN ((RR..AA..))::
This Celestial
version of longitude is measured in units
of hours (hr), minutes (min), and seconds
(sec) on a 24 hour "clock" (similar to how
Earth's time zones ar determined by
longitude lines). The "zero" line was
chosen to pass through the constellation
Pegasus, a sort of cosmic Greenwich
meridian. R.A. coordinates range from
0hr 0min 0sec to 23hr 59min 59sec.
UNDERSTANDING CELESTIAL
MOVEMENTS AND COORDINATES
Understanding where to locate
celestial objects and how those objets move
across the sky is the key to enjoying the
hobby of astronomy. Most amateur
astronomers practice "star-hopping" to
locate celestial objects. They use star
charts or astronomical software to identify
bright stars and star patterns as
"landmarks" in their search for
astronomical objects. Another technique for
locating objects is to use the setting circles
that are provided on your telescope.
UNDERSTANDING HOW CELESTIAL
OBJECTS MOVE
Due to the Earth's rotation, celestial bodies
appear to move from East to West in a
curved path through the skies.
All stars and celestial objects are mapped
onto an imaginary sphere surrounding the
Earth. This mapping system is similar to
the system of latitude and longitude on
Earth surface maps.
6
Looking at or near the Sunwill cause irreversabledamage to your eye. Do not point this telescope at or near the Sun. Do not look through the telescope as it is moving.
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