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Tahsiri: Lecture notes :

Kenealy: Read chapters (1-6).

Please click on the Virtual library www reference guides after the red arrow for further Discussions and Illustrations on the important terms relevant to my lectures.

1) The Moving Sky

* The stars, planets, and Moon appear to move westward during the night. This westward motion can be detected in about a minute.

* Most stars rise and set, but stars in the circumpolar zone centered near Polaris always remain above the horizon. These stars appear to spin counterclockwise about Polaris.

* Stars not located in the circumpolar zone move on circles that carry them below the horizon.

a) Illustrations(1) Circumpolar stars (2) Circumpolar Stars

2) The Terrestrial Coordinate System

* Coordinates: are a set of numbers that uniquely locate a particular place. Everyone who uses a coordinate system must agree on its zero point and the way the measurements are made. We can locate ourselves on the Earth using the terrestrial coordinate system.

* Latitude: describes angular distance north or south of the equator and

* Longitude: describes angular distance east or west from the prime meridian.

* Prime Meridan: The circle on the Earth's surface that runs from pole to pole through Greenwich, England. The zero point of longitude occurs where the prime meridian intersects the Earth's equator

b) Illustrations(1) Latitude and Longitude (2) Explain Latitude and Longitude (3) Coordinate system. (4) Celestial Coordinate System (4) Equator(6) Quiz on Latitude and Longitude (7) Maps (8) Angular Distance (9) Angular Distance (10) Angular Distance (11) Prime Meredian

* The sky above us looks like the inside of a bowl called the celestial sphere. Positions and sizes of stars and other celestial objects in the sky are conveniently described using angles.

c) Illustrations(1) Celestial Sphere (2) The Celestial Sphere and its Points (3) Explain Celestial Sphere

* Angles are often measured in degrees, minutes, and seconds of arc.

* A convenient coordinate system for locating stars and other celestial objects is the horizon system.

* The Horizon system is used to locate stars and other celestial objects.

* Altitude: is the angular distance of the star above the celestial horizon.

* Azimuth: locates the point on the horizon below the star.

d) Illustrations(1) Altitude (2) Azimuth. (3) Define Asimuth (4) Celestial horizon. (5) Horizon System (6) Horizon system.

1. The fist, held at arm's length, fills an angle of about 10 degrees.

2. On the celestial sphere, the circle which is located 90 degrees from the zenith is the horizon.

3. The point directly over an observer's head is that observer's zenith.

4. The angular distance of an object from the horizon is its altitude.

5. The azimuth and altitude of an object located due south and on the horizon are azimuth 180 degrees, altitude 0 degrees.

6. Which of the following would be the coordinates of a star which is setting in the northwest? Azimuth 300 degrees, Altitude 0 degrees.

7. What are the altitude and azimuth (in degrees) of a star which is setting in the west? Altitude 0, Azimuth 270.

8. How many seconds of arc are there in a degree? 3600.

9. During a night, the stars move generally westward.

10. The prime meridian is a line of constant longitude.

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