Astronomy is a nocturnal activity

1953, T. E. Houck and A. D. Code

The sky above us

Stars dominate the night sky

• Relative positions of stars remains fixed• The whole pattern revolves around us• Constellations – patterns in star

distribution• Constellations vary – related to mythology• Constellations not real• 1929 IUA – 88 official constellations• Every star belongs to a constellation

Orion Constellation

Map of Orion Constellation

The wanderers

• Sun, Moon, planets move relative to stars

• Wander in a narrow band – Zodiac

• Ecliptic

The Zodiac

The Ecliptic

The Celestial Sphere

23.5

Earth’s prograde rotation

Ursa Minor

Precession of Earth’s spin

26,000 years period

Equatorial Coordinates

Examples

• Orion:

• Right Ascension: 5 hours

• Declination: 5 degrees

• Ursa Major = Saptarshi Mandal

• The Great Bear (Big Dipper)

• Right Ascension: 11 hours

• Declination: 50 degrees

Image Sources

Image Sources

http://fourmilab.ch/yoursky/

Image Sources