Chapter 2.1 Notes

Chapter 2:

Discovering the universe for yourself

Constellations

A region of the sky with well-defined borders.(There are 88 official constellation).

North Celestial Pole

The point directly over Earth's North Pole.

South Celestial Pole

The point directly over Earth's South Pole.

Celestial Equator

A projection of Earth's equator into space, makes a complete circle around the celestial sphere.

Ecliptic

The path the sun follows as it appears to circle around the celestial sphere once each year.

(Ecliptic crosses the celestial equator at 23 1/2 degree angle(also the tilt of the Earth's axis)

Horizon

The boundary between Earth and the sky.

Zenith

The point directly overhead.

Meridian

An imaginary half-circle stretching from the horizon due south, through the zenith, to the horizon due north.

(Azimuth - Degrees clockwise from due north)

Angular Size

(Of an object) is the angle it spans in your field of view.

Angular Distance

(Between a pair of objects in the sky) is the angle that appears to separate them.

Arcminutes

Subdivide each arcminute into 60 arc seconds

Circumpolar

Remains above the horizon and makes daily counterclockwise circles around the north celestial pole.

Latitude

Measures North-South position.

Longitude

Measures East-West position.

(Local sky varies with Latitude but it does not vary with Longitude.)

(The Altitude of the celestial pole in your sky is equal to your Latitude.)

Zodiac

The constellations along the ecliptic.

(Includes 13 constellations)