Astronomy Lab - Star Charts

OBJECTIVES: Hold a star chart correctly to observe the stars. Define and use the terms horizon and zenith. Correctly hold and orient a star chart and use it to find stars and constellations. Locate constellations on a star chart by star hopping. Identify the zenith and the horizon on a star chart and on the sky. From a star chart, describe the direction and approximate altitude of a star. From a star chart, describe where to look on the sky for a given constellation. Practice using the fist method to locate objects on the sky. Describe the magnitude scale for brightness of stars. Locate the North Star, hence north. Set up an observing session plan for a stargazing trip.

BEFORE YOU COME TO LAB: Enter the title “Star Charts” at the top of a right hand page. Enter the title and page number in your Table of Contents. Enter the date you work on this exercise. Enter the objectives above into your notebook (copy or cut and tape). Enter “PREPARATION”. Under it, write “horizon” and “zenith” along with a definition or description of each. Also enter the reference where you found that information. Enter “PARTNERS” and under it write the names of your partners you work with today.

BRING TO LAB: 1. Your lab notebook, prepped as described above 2. This lab write-up (printed or on a screen) 3. Pen 4. Star chart handed out in lecture (instructor will have extras or you can print one here: http://www.skymaps.com/downloads.html

PROCEDURE IN LAB Use your star chart provided by the instructor in lab or lecture to answer the following questions. Write your answers in your notebook. Put the questions in your notebook too so you or someone else can tell what the answers mean. Make notes to yourself to help you understand what you did and why you answered the way you did.

Fist/Hand Method: (from http://oneminuteastronomer.com/860/measuring-sky/) Your hands and fingers are a remarkably accurate (and convenient) measuring tool. When you hold your hand at arm’s length, you can estimate angles like this: • Stretch your thumb and little finger as far from each other as you can. The span from tip to tip is about 25 degrees • Do the same with your index finger and little finger. The span is 15 degrees • Clench your fist at arm’s length, and hold it with the back of your hand facing you. The width is 10 degrees. (thumb in front of fingers; 10 degrees from pointer to pinky finger) • Hold your three middle fingers together; they span about 5 degrees • The width of your little finger at arm’s length is 1 degree. Star Charts Page 2 of 2 QUESTIONS 1. On what dates and times can you use the star chart that was handed out? Explain where you found this information.

Magnitudes Hipparchus used a magnitude scale for brightness of 1 to 6. The scale has been modified since then. 2. Name the brightest star on your star chart? About what is its magnitude? Explain why you gave your answer. 3. What is the magnitude (number) of the faintest star on your chart? Again explain. (Answer a number; do not try to find a name) 4. Estimate the magnitude of Polaris. Explain.

Direction and altitude (angle) 5. Where is the horizon on your star chart? Where is the zenith on your star chart? 6. How many degrees are there between the horizon and the zenith in the real sky? Explain your answer by stating the altitude in degrees at the horizon and the altitude in degrees at the zenith. 7. a.) For the dates and times shown on your star chart, use altitude (from horizon or zenith) and direction to describe where to find Vega? Describe 2 more stars listed below. Fall semester students only: Describe where to find b.) Altair and c.) Arcturus. Spring semester students only: Describe where to find b.) Procyon and c.) Capella. 8. How else could you describe the location of a star that is 80 degrees above the western horizon?

Measuring angles 9. Go to the front lobby of the science building (second floor lobby). a.) Measure the altitude of the top of the Basilica from the horizon. Describe how you did this. Start at shoulder height. b.) Measure the horizontal angle between the MCTC sign on the T building and the American flag on the other side of Hennepin Avenue.

Holding a star chart 10. Describe how to correctly hold a star chart so that it matches the sky. Which part of the star chart do you hold closest to you?

Stargazing 11. Describe how to find north using the Big Dipper. Start by describing the location of the Big Dipper with direction and altitude. 12. Facing north, where is east? 13. Write a systematic plan for what you will do to find three different constellations as part of the Stargazing Observation. What will you look for first and where in the sky will you look (use altitude and direction)? What will you look for next and where (use star hopping as well as altitude and direction)? What will you look for next and where (again use star hopping as well as altitude and direction)? A great example is the Big Dipper to the Little Dipper and then pick one additional constellation. Use star hopping or altitude & direction to explain each of the 3 constellations.

Before you leave lab 14. Staple or tape your star chart into your notebook before you leave lab. Fold star chart in half; do not cut the chart out. Make sure you can read the instructions around the circle in case you forget how to hold the star chart.