A properly constructed planisphere is in reality an analogue computer. This computer can solve many of the practical problems related to where and at what times objects in the sky may be observed. For example, a planisphere may be used to solve the following problems:

A. How will the sky appear at a particular date and time?

B. What time of year will a specified object be visible (or rise, or set) at a specified time?

Answer the following questions using your planisphere. Record your answers in your lab notebook as a part of your lab report.

1. What constellations are circumpolar for our location? (That is, what constellations may be observed, in principle, at any time of year?)
2. For today's date, what time will the following constellations rise? ( For uniformity, when will the prominent bright stars which make up the constellation be totally above horizon? )
   a. Orion
   b. Taurus
   c. Perseus
   d. Auriga
   e. Leo
   
3. What time will the following constellations set? ( For uniformity, what time will the indicated bright star or asterism just touch the horizon? )
   a. Bootes (Arcturus)
   b. Hercules (keystone)
   c. Lyra (Vega)
   d. Cygnus (Deneb)
   
4. What time will the following objects be on the celestial meridian? (This is the north/south line on the sky and is where any object is highest in the sky for furthest from the horizon. Technically, this is known as the transit time for the object.)
   a. The Andromeda Galaxy (M31)
   b. The Orion Nebula (M42)
5. What time of year (approximate date) will the bright star Sirius in the constellation Canis Major rise just before the sun. (Assume the sun rises at about 6 am) This phenomenon is termed a heliacal rising. Such a rising of Sirius was used by the Egyptians to foretell the yearly flooding of the Nile. Since Sirius is known to many people as the "Dog Star" this particular phenomenon has become associated with the origin of the term "dog days."
6. The "summer Milky Way" passes through the constellations of Cygnus and Saggitarius. Can you explain the origin of the term "summer Milky Way?" Is there a "winter Milky Way?" Through what constellations does it pass?
7. Looking toward the north, which way does the sky appear to rotate during a single night? Which way does it appear to rotate as the year progresses? Which way will the sky appear to move if you are looking toward the south? (Answer these four questions as clockwise or counterclockwise.)
8. Approximately what fraction of a circle (how many degrees) do the stars appear to move in one month? Approximately how many degrees do the stars appear to move in one hour? To the nearest degree, how many degrees does the sky appear to rotate in 24 hours?
9. Find your sun sign (a zodiacal constellation) on the planisphere. On approximately what date will this constellation be observable all night? Note that for an object to be observable all night, it should rise at sunset (approximately 6 pm) and set at sunrise (approximately 6 am). Note also that this means the object will be on the celestial meridian at midnight. Technically, this phenomenon is termed the date of culmination.
   What is the relation of this date to your birthday? Try to explain this relationship. Also try to find the dates associated with your sun sign by popular astrology. How do these three dates compare? We will consider these dates in a subsequent laboratory project.

THIS PAGE CREATED BY NGS