USING YOUR STAR CHART

OBJECT: To learn how to use your star chart as an aid in seeing how the Sun, the stars, and the planets move across the sky.

PROCEDURE: 1) a) Locate the four standard directions of North, East, South, and West on the Star Chart. Note that they go in reverse order from what you usually see on a map. This is because to use the Star Chart, you must hold it over your head and look at it upside down. b) Locate the zenith (it is NOT marked).

2) Locate the constellations of the Zodiac on your star chart. (These twelve constellations are located on a (dotted) line called the ecliptic. The twelve constellations (in order) are: Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Sagittarius, Capricornus and Aquarius.

Question #1: Does the above order proceed from East to West, or from West to East?

3) Locate the North Star. (Hint: the North Star is the only star that does not change its position during the year or during the night.)

Question #2-a: About how high (in degrees) above the horizon is the North Star here in Memphis? (The horizon is at 0, the zenith is at 90.) Question #2-b: At the North Pole, how high (in degrees) above the horizon is the North Star? Question #2-c: At the earth's equator, how high (in degrees) above the horizon is the North Star? Question #2-d: If you did not know your location, could you tell your latitude (in degrees) by observing how high (in degrees) the North Star is above the horizon at your location?

4) Locate the position of the celestial equator on the star chart: it is a circle whose center is the North Star and which crosses the ecliptic at two places: March 21 and Sept 21. Note also that the ecliptic (identified in step 2 above) is not equidistant from the North Star: it is half the time above and half the time below the equator.

5) a) Locate the big dipper. (Hint: it is about 2/3 the way from the equator to the North Star.) b) Now locate the two pointer stars on the Big Dipper (these two stars point toward the North Star).

6) a) Note the calendar days on the movable circle and the hours of the day on the stationary part of the chart. b) Rotate the movable circle so that the calendar day for today is matched up with 8 p.m. Now locate the big dipper and note its position relative to N,E,S,W, and the zenith.

Using Your Star Chart 2

c) Now rotate the movable circle so that the time is changed to midnight. Again locate the big dipper and note its new position relative to N,E,S,W, and zenith.

Question #3-a: Could you tell time by watching the big dipper move across the sky (assuming of course that the sky was clear so you could see the stars) ?

d) Now rotate the movable circle so that the time is 8 pm three months from now. Again locate the big dipper and note its new position relative to N,E,S,W, and zenith.

Question #3-b: Could you tell what month it is by observing the position of the Big Dipper at 8 p.m. ?

7) The position of the Sun and the planets are not specified on the star chart. This is because the Sun and the planets seems to move in relation to the stars. Even though the Sun moves, it does not wander around aimlessly or without bounds. In fact, the Sun moves along a line in the sky called the ecliptic - the same ecliptic that the constellations of the zodiac lie on. In fact it is this fact of the Sun moving along this line that makes the twelve constellations of the zodiac special. a) Locate the present position of the Sun on your star chart. b) Now locate the position of the Sun one month from now.

Question #4-a: Does the Sun move along the ecliptic in an East to West or West to East direction? Question #4-b: How long does it take the Sun to make one complete circuit of the ecliptic?

c) Locate the position of the Sun on your birthday.

Question #5-a: What day is your birthday and in what constellation does the Sun appear to be in on that day? Question #5-b: Is this constellation the same one that astrology has assigned to you? [Astrology was set up 2000 years ago, and because of something called "precession of the equinoxes" which we will discuss in part 3, astrology's assignments are about one month (one constellation) off!]

d) Locate the positions of the Sun on the following four days: March 21, June 21, September 21, and December 21.

Question #6-a: Can you determine what makes these days special? (These days are close to the days that mark the four official seasons of spring, summer, fall, and winter. Hint: consider how high above the southern horizon the Sun is at noon on each of these four days.)

e) Determine the time and the position of the rising and the setting of the Sun on each of the four days specified in part d above.

Question 6-b: Wat is special about the above times and positions for each of the four days? (Hint: note how far South or North the position of the rising and setting of the Sun is from due East and due West respectively for each of the days.) Using Your Star Chart 3

8) The moon also does not appear on the star chart. As we will see later when we look at the moon more closely, the moon also moves on a path that is very close to the ecliptic. Also, a full moon rises in the East just as the Sun sets in the West (that is, it is opposite the Sun).

Question #7: Based on this information and your previous responses, during what month of the year should the full moon be highest in the sky at midnight?

9) Rotate your star chart back to what it should be for this evening at about 8 p.m.

Question #8-a: What constellations will appear near the zenith? Question #8-b: Identify the brightest stars that will be in the sky this evening, and note in which constellations these stars are in. It is sometimes easier in the city to see the bright stars and build the constellations around them than identify the constellations first. Caution: be aware that the planets also move in relation to the stars and that like the Sun and moon they are found on or near the ecliptic - so don't be fooled by the present of a bright light in the sky that doesn't match your star chart - it may be a planet if it is located near the ecliptic.

REPORT: Answer in full sentences all of the questions posed in the procedure part of this lab.