Meade 114EQ-AR instruction manual Understanding Celestial Movements and Coordinates

Meade114EQAR 3/28/07 9:52 AM Page 8

UNDERSTANDING CELESTIAL

6MOVEMENTS 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.

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 Right Ascension and Declination.

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°).

•RIGHT ASCENSION (R.A.): 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.

Looking at or near the Sun will cause irreversable damage to your eye. Do not point this telescope at or near the Sun. Do not look through the telescope as it is moving.