Astronomy 30, Observing #3 Name: Lab Partners: Date: Materials: This lab, with the star chart completed from the pre-lab. Some sheets of paper for sketches. A pencil with eraser. A small flashlight, ideally with either a red bulb, or some red cellophane taped over the light (that helps to preserve night vision). Warm clothes!!! INDOORS: Before we go out, look at the various coordinate figures near the end of lab, which illustrate aspects of three different coordinate systems that we use. Local Coordinates. These are centered upon you, the observer. Terrestrial Coordinates. These are centered upon, and used to locate things on, Earth. One major reference is the equator, which divides Earth into northern and southern hemispheres. The other is the Prime Meridian, which runs through Greenwich, England, and divides Earth into eastern and western hemispheres. Distance north or south of the equator is measured in angles of latitude. Distance east or west of the Prime Meridian is measured in degrees longitude. Celestial Coordinates. Those are used to locate objects on the Celestial Sphere, which is an imaginary Sphere surrounding Earth. Declination measures angles north or south of the Celestial Equator, which is the projection of Earth s equator onto the sky. Angles eastward are measured using Right Ascension, starting from the Vernal Equinox. The final figure shows the relation between the Ecliptic and the Celestial Equator. The Ecliptic is the path that Sun appears to follow through the sky over the course of one year. Now, answer the following questions:
1) What line on the sky does the Sun cross at noon (think of local coordinates)? 2) Yellowknife, Canada is almost due North of us. Would the Zenith for an observer in Yellowknife point at the same point on the Celestial Sphere at 10 pm as it does for an observer in Livermore? Why or why not? 3) How far above the horizon would the North Celestial Pole be if you lived on the equator? How about if you lived at the North Pole? Using those differences, how far above the northern horizon would we see the North Celestial pole? Livermore is at approximately 38 degrees North latitude. 4) Repeat your reasoning above to determine how far above the horizon the Celestial Equator will be where it crosses the meridian, as viewed in Livermore. Zodiacal constellations are of no special significance to astronomy. They are assigned special significance in astrology because the Sun, Moon, and planets appear to pass through them. 5) Why do the Sun, Moon, and planets all follow the ecliptic in the sky? 6) What determines the tilt of the Ecliptic relative to the Celestial Equator?
7) Which way does the Sun move along the Ecliptic, east-to-west, or west-to-east. This can be a bit of a brain twister, and you may want to act it out. 8) Look at the star chart at the end of the lab. Which Zodiacal constellations might we be able to see tonight? 9) What constellations does the Celestial equator pass through on the part of the sky that is visible tonight? 10) One of the equinoxes is above the horizon tonight. Which one is it? In what month of the year would the Sun be at that equinox? OUTDOORS: A) Constellations From last time, point out to me Cassiopeia, the Big Dipper, and show me how to find Polaris. Look to the South, and point out to me Orion, the Winter Triangle, and name the stars that make up the Winter Triangle. Then point out Leo, Gemini, and Taurus. Indicate to me the path of the Ecliptic and the Celestial Equator from the pre-lab. Once you ve done all of this, get my initials here. Now identify as many of the Zodiacal constellations as you can, and point them out to me. Also indicate for me the approximate location of the equinox that is in the sky tonight. You might need aides to finding some of the Zodiacal constellations. Leo, Gemini, and Taurus (if it s still up) are no problem. Cancer is very hard to see from our location. Look for a few faint stars between Leo and Gemini. Virgo is also difficult, though it has one bright star, Spica. To find Spica, start from, of all things, the Big Dipper. Follow the arc of the handle of the Big Dipper away from the bowl. You will come to a bright red star, Arcturus (the phrase astronomers use to remember this is, Follow the arc to Arcturus ). Continuing along that path ( Speed on to Spica ), you will come to a bright blue star, with no bright stars around it. That s Spica.
Once you ve shown me the Zodical constellations and the location of the equinox, get my initials here. B) Look through a telescope If I can find them, I ll show you h and chi Perseii. Sketch them, and answer the following: 11) What are h and chi Perseii (a Google search should give plenty of information)? HAND IN YOUR RESULTS NEXT WEEK This is an informal lab report. Hand in these sheets, plus any other ones that you used. Make sure to include the pages with my initials, the star chart that you completed in the pre-lab, your sketches, and the answers to the questions.