University of Michigan - Department of Astronomy

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Version: sphere


Coordinate Systems on the Celestial Sphere

Part 1: Using the Celestial Sphere

Identify the following things on the celestial sphere: equator, ecliptic, north celestial pole, horizon, and meridian on the celestial sphere.

  1. Which of those is/are engraved on the plastic sphere?


  2. Which is/are represented by the metal frame?


  3. Which ones do you need to measure RA and dec?


  4. Which ones do you need to measure the alt-az?

Adjust the sphere to show the stars at your latitude by changing the altitude of the north pole to your latitude (~42°).

Your GSI will give you two stars, one in the north and one in the south. If you did the planetarium version, use the same stars. Record their names in table 3. Identify the two stars on the celestial sphere.

  1. Rotate the sphere until the first star is the farthest east of the meridian that it gets (spin the sphere around to find that position.) Record its altitude, azimuth, right ascension and declination in table 3.
  2. Rotate the sphere until the first star is on the meridian and make the measurements again.
  3. Rotate the sphere until the second star is just rising. Record its altitude, azimuth, right ascension and declination in table 3.
  4. Rotate the sphere until the second star is on the meridian and make the measurements again.
Table 3: Coordinates Using the Celestial Sphere
Star Position Alt (deg) Az (deg) RA (hr:min) Dec (deg)
  1        
2        
  1        
2        

Identify the stars in the Big Dipper.

  1. What is the range of declination of the Big Dipper?


  2. Stars that never rise and set, like the Big Dipper, are called circumpolar. Is the Big Dipper circumpolar from everywhere on the planet? Explain.

Last modified: 4/30/10 by SAM

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