1. Constellations Astronomy: A pattern of stars Astrology
6000 visible stars
No physical proximity
The sky appears as 2-dimensional
Astrology
Origins of many cultures
Storytelling / folklore
Seasonal Events: planting, harvest, floods, drought, religious/cultural events
Pre-dates calendars
88 Constellations – North & South Hemispheres

2. Orion in 3-D

3. Orion: The Hunter

5. Orion: The Hunter Due South @ 9 pm tonight
Betelgeuse, Rigel, The Orion Nubula (Orion’s Sword)
Orion stands by the river Eridanus accompanied by his faithful dogs, Canis Major and Canis Minor, hunting various celestial animals, including Lepus, the hare, and Taurus, the bull. Orion was in love with Merope, one of the Seven Sisters who form the Pleiades, but Merope would have nothing to do with him. Orion's tragic life ended when he stepped on Scorpius, the scorpion. The gods felt sorry for him, so they put him and his dogs in the sky as constellations and all of the animals he hunted up there near him. Scorpius, however, was placed on the opposite side of the sky so Orion would never be hurt by it again.

6. Celestial Coordinates: Extension of the Earth’s Coordinates
FIXED positions
North celestial pole
(known as “Polaris”)
South celestial pole
Celestial equator

7. Right Ascension & Declination Analogous to Longitude and Latitude
Right Ascension (RA) measured Eastward in hours and minutes from the position of the sun at vernal the equinox (Spring) o / 24hr = 15o / hr
Declination (dec) measured in degrees north or south above the celestial equator.

9. Horizon System: Sky Coordinates
Zenith: point directly overhead at any time
Horizon: the lowest point you can see (the ground)
Meridian: N / S line dividing the sky into E - W
Altitude: angular distance above horizon
Azimuth: compass direction
North = 0o
East = 90o
South = 180o
West = 270o
Altitude = 60o Azimuth = 135o
Nadir: directly downward

10. Daily or diurnal motion
- Apparent westward motion of sun, moon, planets, stars in the sky
Earth rotates on its own axis
every 24 hours in an
EASTWARD direction
(from above counter clockwise)
To us, it appears as if
objects in the sky are
moving WESTWARD—
Sun rises in the E
Sun sets in W

11. Check your knowledge--
The position of Polaris, the “North Star”,
in the night sky in the United States:
(a) is always directly overhead
(b) is always near the horizon
(c) is at 23.5 degrees from the horizon
(d) depends on your location
ANSWER: (d)

12. The background stars move 1o westward per day resulting in the same star rising 4 minutes earlier each day.

13. As Earth orbits our Sun, different constellations are visible at different times of the year.

14. Position of sunrise and sunset changes due to the orientation of the Earth with the Sun
Sun rises North of East in Summer Sun sets North of West in Summer
Sun sets South of East in Winter Sun sets South of West in Winter

15. Using the Planisphere Location of stars and constellations in the sky
Constellations in the zodiac
The ecliptic (path of the sun) and celestial equator
Position (azimuth) and time of sunrise and sunset
Location & visibility of planets