Celestial Sphere Review

Multiple Choice

How long does it take a star to get back to the same position in the sky it was the night before?

• 24 hours exactly
• 24 hours and 4 minutes
• 23 hours 30 minutes
• 23 hours 56 minutes

The Celestial Sphere

The Celestial Sphere

•The “Celestial Sphere” is an ancient concept dating back to the time
when we thought the earth was the center of universe

•It is a “gigantic” sphere glued to the stars

•Stars appear to rotate because sphere is rotating

•Sun, Planets, Comets, Asteroids all move on surface of sphere

Images taken from http://zebu.uoregon.edu/~imamura/121/images/sphere.gif

​The right shows our view of the celestial sphere on the left. We will focus on OUR view of the celestial sphere.

Multiple Choice

An imaginary dome of the sky onto which all celestial objects such as stars, moons and planets can be plotted.

• Sun

• Celestial Sphere

• Apparent Motion

• Real Motion

Multiple Choice

The ___ is found in the center of the celestial sphere.

• Sun

• Moon

• Solar System

• Earth

Multiple Choice

Degrees are divided in smaller parts called...

• hours (arc hours).
• minutes (arc minutes).
• seconds (arc seconds).
• milliseconds (arc milliseconds).

Multiple Choice

Arc minutes are divided in smaller parts called...

• hours (arc hours).
• minutes (arc minutes).
• seconds (arc seconds).
• milliseconds (arc milliseconds).

Celestial Sphere “Parts” You are reviewing today

▪ Meridian
▪ Celestial sphere
▪ Zenith
▪ Nadir
▪ Celestial poles
▪ Azimuth
▪ Altitude

Zenith

▪If you place yourself in the middle
of the celestial sphere, the zenith
is directly above you….90° above
your head

Horizon

▪The intersection of the celestial
“dome” and earth….

Note your cardinal directions….

Multiple Choice

__________ is the point directly below the observer.

• Zenith

• Nadir

• Meridian

• Horizon

Multiple Choice

Name the point directly above an observers head

• North Celestial Pole

• Nadir

• Zenith

• Polaris

Multiple Choice

If an astronomer informs you that a constellation is at the zenith, where would you look for it?

• northern horizon

• southern horizon

• directly overhead

• eastern horizon

But WHERE is the NCP and
the SCP?


It is the geographical latitude
latitude of the observer.

In Pocatello, you are a latitude of 42.9°. What is the degree of the Celestial North Pole (CNP)?

​42.9

Altitude of NCP is always equal to your latitude on Earth's surface.

Multiple Choice

An observer sees Polaris at 43 degrees altitude, what is the observer's latitude?

• 0 degrees

• 43 degrees

• 47 degrees

• 90 degrees

Multiple Choice

An observer starts at the equator, and moves 25 degrees North Latitude, where would they find Polaris?

• 25 degrees Altitude

• 25 degrees Azimuth

• 65 degrees Altitude

• 65 degrees Azimuth

RIGHT NOW…your celestial
north pole happens to be a star
called Polaris.

Multiple Choice

Will Polaris always be at the NCP? (North Celestial Pole)

• Yes, it will always be the NCP

• Yes, although this changes based on your latitude

• No, because of the earth's revolution around the sun

• No, because the earth's axis precession

The sky appears to rotate around NCP.

Multiple Select

The star that is currently closest to the North Celestial Pole is:

• Arcturus
• Betelgeuse
• Polaris
• Rigel
• Nicole Kidman

Multiple Select

In the Northern Hemisphere, the altitude (height in degrees above the horizon) of the North Star is always roughly equal to the

• longitude of the observer
• latitude of the observer
• altitude of the Sun
• the tilt of the Earth's axis
• the temperature at midnight

Multiple Choice

If you were standing at the North Pole, Polaris will be ___.

• on the northern horizon

• below the horizon

• at your zenith

• to the north at an altitude equal to your latitude

Celestial Equator – imaginary circle
cutting the meridian in two equal
parts going through the observer
and the meridian.

Multiple Choice

What is the celestial equator?

• A band of constellations through which the planets and sun appear to move.

• The line that the sun traces across the celestial sphere.

• An imaginary line in the sky directly above Earth's equator.

• An imaginary line running north-south through the zenith

Multiple Choice

The Celestial Sphere spins around two points in the sky known as the.....

• North and South Poles.
• Celestial North and Celestial South Poles.
• East and West Points of Light.
• Arctic and Antarctic Points.

Now you know the celestial sphere
terms….What do you do with them now?

▪FIND PLACES!!!

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▪Latitude, altitude and azimuth
are measured in degrees.

▪There are 360° in a circle and
each degree can be further
equally subdivided

Multiple Choice

An object due west would have an azimuth of...

• 0 degrees

• 90 degrees

• 180 degrees

• 270 degrees

Multiple Choice

Which of the following is the angle measure from North in the horizontal direction?

• Azimuth

• Zenith

• Altitude

• Longitude

Multiple Choice

The horizon has an altitude of...

• 0 degrees

• 5 degrees

• 45 degrees

• 90 degrees

Multiple Choice

The angle measure upward from the horizon

• Azimuth

• Zenith

• Altitude

• Latitude

Limitations of Local Coordinates

• For an observer, all stars and objects in

sky besides North and South Pole stars
have Altitude and Azimuth that are
constantly changing

• Two people at different spots on earth

will disagree about Altitude and
azimuth coordinates even if they are
looking at the same object at the same
time