.Celestial Sphere
- stars seem to move across the sky as though they are on the inside of a giant ball – this is the celestial sphere.
- the northern tip is called the North Celestial Pole. The southern tip is the South Celestial Pole.
- the celestial sphere appears to rotate on an axis that runs between its two celestial poles.
- there is an equator around the middle of the celestial sphere, just like Earth’s.
- the zenith is the point on the sphere above a person’s head as they look into the night sky.
- the zenith is the point on the sphere above a person’s head as they look into the night sky.
- the position of the stars on the celestial sphere are given by their declination (Dec.) and right ascension (R.A.) (See below).
- Declination (DEC)
DEC is like latitude. It is measured in degrees and shows a star’s position between the pole and the equator. - Right ascension (RA)
RA is like longitude. It is measured in hours, minutes and seconds, and shows how far a star is from the First Point of Aries
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