Sky Motion & the Stars

This sheet of questions goes with the packet handed out in class including information from Star-Finding with a Planisphere by Alan M. MacRobert and The Edmund Sky Guide by Terence Dickinson and Sam Brown.

Answer the following questions based on the handout. Use complete sentences in your answers: some answers will require frequent returns to the text to figure out and you will need to use more than one sentence in some cases.

1. What does the word planisphere mean?
2. What is the purpose of a planisphere?
3. In your own words describe how to set the planisphere for a particular date and time.
4. What do the edges of the star map stand for in the real world?
5. How do you have to hold a planisphere to view the stars in the East? Why?
6. Which side of the planisphere is the one where the stars rise? On which side do they set? Refer to the cardinal directions (North, East, South, and West).
7. How many degrees of sky are there between the point marked North and the point marked South? Where on the line between N and S is the Zenith?

8. What bright constellations are rising at 7:00 pm tonight? Include only those on your list marked as bright and those within about one half inch of the eastern horizon.
9. What bright constellations are setting at 7:00 pm tonight? Include only those on your list marked as bright and those within about one half inch of the western horizon.
10. What bright constellations are transitting at 7:00 pm tonight? Include only those on your list marked as bright and those within about one half inch of an imaginary line drawn from due North to due South. (To transit in Astronomy means to reach the highest point in the sky that an object can reach. This always happens due South for observers in the Northern Hemisphere).
11. Where would you have to look to see the stars directly in the middle of the planisphere when you hold it with East down? Also, what is this position on the planisphere’s sky map called?
12. Where would you have to look to see the stars within ½ inch of the Western horizon of the planisphere when you hold it with East down?
13. How do you correct for Daylight Savings Time when you use the planisphere?
14. Why does the sky appear to move overhead over the course of a night? That is, explain why stars rise in the East and set in the West. Using a globe may help with this question.
15. There is a star on the planisphere that does not appear to move as you turn it. What star is it and why does it stay in place?
16. What makes the star called Polaris (the North Star) special? Is it the brightest star in the sky? (answer both questions!)

17. Look at the constellations near Polaris on your planisphere. Choose two of the bright constellations and try to find out when they rise and set on today’s date. Describe the motion of these constellations over the course of twenty-four hours.

Define the following terms in your own words.

1. celestial sphere:
2. north celestial pole:
3. zenith:
4. rise:
5. set:

6. transit:
7. horizon:
8. constellation:
9. axis of rotation: