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# Part 1: Determining an object's position in the sky with the "Horizon Coordinate System"

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1.     [6 pts] Set the location to Fairfax or Washington, DC and record your latitude and longitude. Set the time to 10 PM the day you do the lab.

Latitude:

Longitude:

2.     [4 pts] Search for the North Star "Polaris". What are altitude and azimuth of Polaris?

Altitude:

Azimuth:

3.     [4 pts] How does this compare to the latitude of your current location (Fairfax, Washington DC)?

4.     [6 pts] List the names of all constellations you can see from your location:

5.     [5 pts] What are the stars that belong to "Cassiopeia"? Click on them, record their names, and estimate their positions (altitude and Azimuth). Format hint:

[Insert table here]

Part 2: Determining an object's position in the sky with the "Equatorial Coordinate System" -

Stars are represented by small circles of various sizes.  The larger the circle appears, the brighter the star.

6.     [2 pts] What is the name of the brightest star in the constellation of Cygnus?

Star Name

Altitude

Azimuth

Right Ascension

Declination

7.     [2 pts] What is the name of the brightest star in the constellation of Lyra?

Star Name

Altitude

Azimuth

Right Ascension

Declination

8.     [12 pts] Complete the table below.

Star Name

Constellation Name

Right Ascension

Declination

Arcturus

Sirius

Altair

Pollux

Procyon

Rigel

Part 3: Sunset and Sunrise

9.     [3 pts] Set the location to Fairfax for today's date at noon:

10.  [3 pts] What is the Sun's altitude at noon?

11.  [3 pts] What direction would you face in order to see the Sun at noon?

12.  [5 pts] Set the time to today and 12 PM. Fast forward the time to find how many hours after 12 PM sunset occurs.  (Give your answer to the nearest ½ hour)

13.  [5 pts] What is the Sun's altitude now (i.e. at sunset)?

14.  [5 pts] What direction would you face to watch sunset today?

15.  [6 pts] List two stars that are just rising in the East at sunset today.

Star Name

Constellation

Right Ascension

Declination

Altitude

Azimuth

16.  [6 pts] Now change the time to 3 hours past sunset and record the altitudes and azimuths of the stars you listed above and record the result in the table.

Star name

Constellation

Right Ascension

Declination

Altitude

Azimuth

17.  [4 pts] Does the Sun rise due east every day? Set due west?

18.  [5 pts] On which day does the Sun rise farthest to the north?

Part IV: Practice Problems

Exercise 1 [4 pts]:

It is noon on the 20th of May.  You and a group of friends are sailing around the world.  On this particular day you decide just for fun to use a sextant to measure the alti­tude of the Sun and compare it to your known location.  The Sun is to the south and you measure its altitude to be 75º.  What is your latitude?  Explain how you figured this out. (Hint: you will need to look up the declination of the Sun for May 20th)

Exercise 2 [4 pts]:

Using the program Stellarium, locate the position (right ascension and declination) of Mars for the day of your lab.  Write down the constellation it appears to be in.  Explain where you expect Mars to be a month from today and why you expect it to be where you predict.

Part V: Conclusion [6 pts]:

If you were an astronomer and needed to communicate about an object such as Vega to a fellow astronomer in Denver, what coordinates would you use to describe Vega's position? Why? Explain

Evaluate if you have achieved the learning goals given at the first page of the lab handout.

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