200 likes | 352 Vues
Apparent Celestial Movements. What are Celestial objects?. The things seen in our sky that are outside of the Earth’s atmosphere. Sun Moon Stars Planets. What is a Celestial Sphere?. The dome of night sky above your location extending from strait up to the horizon 360 degrees around.
E N D
What are Celestial objects? • The things seen in our sky that are outside of the Earth’s atmosphere. • Sun • Moon • Stars • Planets
What is a Celestial Sphere? • The dome of night sky above your location extending from strait up to the horizon 360 degrees around. • We can use this to determine locations of celestial objects
How do we measure celestial object locations? • Using the: • Zenith • Azimuth • Altitude
Zenith • The point directly overhead, 90 degrees from the horizon.
Azimuth • Uses compass directions • Expressed as an angle measured from North (being 0 degrees), clockwise to East (90 degrees), clockwise to South (180 degrees), to west (270 degrees), and around the horizon back to 360 degrees.
Altitude • The angle above the horizon from 0 to 90 degrees.
The Sun in the celestial sphere • Day and night • Solar noon • Sun’s path with the changing seasons • Location- Latitude, Longitude
Day and Night • The Earth rotates on it’s axis causing day and night. • 24 hours = 1 rotation of Earth on it’s axis • As the Earth rotates it goes in and out of sunlight once per rotation
Why do we experience different amounts of daylight through the year? • The 23 ½ degree tilt of the earth’s axis: • Summer solstice (June 20)- Northern hemisphere tilted toward the sun will have more then 12 hours of daylight. • Winter solstice (December 20)- Northern hemisphere tilted away from the sun will have less then 12 hours of daylight • The equinoxes (March 23 and Sept. 23)- 12 hours of daylight, 12 hours of darkness.
Evidence supporting rotation • The Coriolis Effect (wind deflection) • Movement of a pendulum • Satellite images http://www.classzone.com/books/earth_science/terc/content/visualizations/es0403/es0403page01.cfm?chapter_no=visualization
What is Solar Noon? • Sun’s highest point in the observers sky • Found by finding the mid point between sunrise and sunset
Summer Solstice • Sun rises in ENE • Sun sets in WNW
Equinox’s • Rises in the East • Sets in the West
Winter Solstice • Rises ESE • Sets WSW
Changes with Longitude • Earth rotates counterclockwise 15 degrees per hour • 15 degrees /360 degrees = 24 time zones • Move 1 hour from zone to zone.
Changes with Latitude • Equator – 12 hours of daylight everyday • Mid and upper latitudes depend on the season http://www.daylightmap.com/?hl