What is the celestial sphere? How much of the sphere does an observer on Earth see at any location? What is the ecliptic?

• The celestial sphere is an imaginary sphere of arbitrarily large radius, concentric with Earth.

• An observer on Earth can see half of the celestial sphere at any location.

• The ecliptic is the apparent path of the Sun on the celestial sphere.

• All of the above.

Know the definitions of horizon, zenith, altitude, and azimuth.

• Horizon is the line where the earth's surface and the sky appear to meet.

• Zenith is the point in the sky directly above an observer.

• Altitude is the angle between an object in the sky and the observer's horizon.

• Azimuth is the angle between the north point and the perpendicular projection of the star down onto the horizon.

What is the celestial meridian? What is solar noon?

• The celestial meridian is an imaginary line in the sky that divides the eastern and western halves of the celestial sphere. Solar noon is when the sun is at its highest point in the sky.

• The celestial meridian is the path of the sun across the sky. Solar noon is the time when the sun rises.

• The celestial meridian is a line that connects the North and South Poles. Solar noon is when the sun sets.

• The celestial meridian is a line that runs parallel to the equator. Solar noon is when the sun is at the horizon.

What instrument measures altitude?

• Barometer

• Altimeter

• Thermometer

• Hygrometer

Know the azimuth values in degrees for the directions north, south, east and west, and be able to estimate the azimuth values and directions between them.

• North: 0°, East: 90°, South: 180°, West: 270°

• North: 90°, East: 180°, South: 270°, West: 0°

• North: 180°, East: 270°, South: 0°, West: 90°

• North: 270°, East: 0°, South: 90°, West: 180°

The north star appears to remain stationary in the night sky in the northern hemisphere because:

• It is the brightest star in the sky.

• It is located directly above the North Pole.

• It is part of the Big Dipper constellation.

• It is closer to Earth than other stars.

Polaris can be seen in the southern hemisphere.

• True

• False

The altitude to Polaris is equal to an observer’s ________________?

• latitude

• longitude

• altitude

• time zone

The altitude to Polaris changes as a person drives from New York to the Equator. How does it change?

• It increases

• It decreases

• It remains the same

• It fluctuates

Circumpolar stars are stars that:

• Never set below the horizon

• Are visible only during the day

• Change position rapidly

• Are only visible in the southern hemisphere