IV. Observing Ursa Major (the Big Dipper) version I

(This version takes a few minutes one night every ten days for a month or two.)

1. Pick a time well after sunset when the sky is dark and the Big Dipper and Polaris (the North Star) are clearly visible. It is important that you make all of your observations at exactly the same time.  (You might have to adjust for daylight savings time.)  Make sure that you have a good clear view of a low horizon from your observing location.
2. Using the special polar graph paper provided by the instructor, carefully record the position of the seven stars that make up the Big Dipper.  Note that the stars should not change their distance away from one another or away from the North Star; rather, they should seem to rotate around together in a circle.  Repeat this observation at least four times at ten day intervals.  (The longer span of time used for this project, the better.  You might make observations over two months, if possible.)  Record the date and time of each observation.
3. Special note to photographers. If you have a good camera you might try mounting it on a tripod and taking timed exposures of the sky. Make sure you include Polaris, Ursa Major and some foreground object like a tree or house (for reference later) in the field of view. Depending on the speed of your lens, film/CCD you might try exposures of 10, 30 and 60 seconds. It would be wise to also make a sketch, both to help you with the pictures and in case the pictures don’t turn out.
4. Using your graph paper, measure the total number of degrees that the Big Dipper has rotated around Polaris. Divide 360 by the number of degrees that the Big Dipper has rotated. Next, multiply the result by the number of days between your first and last observations. If you have been careful, your answer should be close to the number of days in a year.
5. Is your result close? If not, why not?

V. Observing Ursa Major (the Big Dipper) version II

(This version takes all night long for one night.)

1. Pick a time well after sunset when the sky is dark and the Big Dipper and Polaris (the North Star) are clearly visible. You will be making measurements all night long, so pick a night with no clouds in the forecast.
2. Using the special polar graph paper provided by the instructor, carefully record the position of the seven stars that make up the Big Dipper.  Note that the stars should not change their distance away from one another or away from the North Star; rather, they should seem to rotate around together in a circle.  Repeat this observation every two hours all night long until nearly sunrise. Record the date and time of each observation.
3. Special note to photographers. If you have a good camera you might try mounting it on a tripod and taking timed exposures of the sky. Make sure you include Polaris, Ursa Major and some foreground object like a tree or house (for reference later) in the field of view. Depending on the speed of your lens, film/CCD you might try exposures of 10, 30 and 60 seconds. It would be wise to also make the careful sketch noted above, both to help you with the pictures and in case the pictures don’t turn out.
4. Determine the average number of degrees of motion per hour. If you have been careful it should be close to 15E per hour. Now, multiply your result by 24 hours this will predict the angle that Ursa Major rotates through in one day. It is highly unlikely that a single night’s measurements will be accurate enough to get exactly the correct answer. The correct answer is 361 degrees, not 360 degrees. Discuss why the correct answer is 361 degrees in your report.
5. Discuss your results in the report and why you think they might be off from the expected results.