Astronomy/Physical Science Activity - Warren Wilson College

This project supported in part by the Appalachian College Association - Teaching and Technology: Stage II - funded by the Andrew W. Mellon foundation. 

Photographic tracking of a planet

Please do not print these instructions!  Save paper!

For this activity you will need the following software:


The word "Planet" in Greek means a "wanderer", because all these bodies wander about the stars in the celestial sphere in a semi-regular pattern.  Photography provides an excellent record of a planet's movement.  We have photographed (with a digital camera) several images of a planet throughout the months of a previous semester.  Current students at WWC will be expected to participate in on-going photography of planets in the current semester as they become visible.  All these images have been aligned by the instructor so that the stars appear in the same position in each image frame.

Here is a brief preview of the activity.

  1. You will download the images from the host site, extract the images, and save them on your local disk drive or network drive.
  2. You will use a program "Irfanview" to view these images, enhance contrast, and to print one as a negative. 
  3. You will make a slideshow to view these images in fairly rapid succession.  In these images, the stars appear stationary while you see the planet "moving" across the field of stars. 
  4. You will plot the position of the planet on different dates on your printed negative and make some conclusions about the apparent motion of the planet.

Procedure - Detailed instructions.  Please follow these instructions closely to avoid losing data.  Keep these instructions open on your computer while executing other programs needed for the assignment.  You will need about one hour of time including downloading and installing Irfanview if needed.  Please do not print these instructions!  Save paper!

  1. Download the images from one of the sites below (more choices will be added in future years).   Be sure to save the file to disk - don't open it.  Each file is a zipped file of several images.  Choose a local directory to store the file.  Use your hard disk if using your own computer, or a server directory if you are in a campus computer lab.  Be sure to make a new directory with the appropriate planet name in which to store these files.  It is important to remember where you download the zipped file.  In the WWC computer Labs, the downloaded zipped files are stored in the users server drive (M:).  After download, the user should move the zipped files to a sub-directory in his/her server drive using a mnemonic name.  One separate directory for a single planet series.

    1. Saturn 2003-2004.
    2. Saturn 2004-2005. - Updated June 14, 2005.  Complete
      1. Note: The Saturn images for April 3, April 14, and April 27, 2005 were contributed by Dr. Jim Warden, Emory and Henry College.
    3. Jupiter 2004-2005. - Complete.  Includes Jupiter from November, 2004 to July 19, 2005
      1. Note: The Jupiter images for April 10, April 14, April 27, May 3, May 8, May 26, and June 5, 2005 were contributed by Dr. Jim Warden, Emory and Henry College
    1. Mars 2005-2006.  - Complete.  Note:  Students Robin Gallagher, Julia Travis, and Brandon Kelley all contributed to the image set.
  1. These are self-extracting zip file or plain zipped files.  Follow the following instructions carefully, and keep these instructions open in order to follow them. 

  2. Open Windows Explorer on your computer.  This is the main file navigation program.

  3. Navigate to the folder where you just saved the zip file.  For best results, be sure to navigate to the folder before extracting.  Do not use the file in the download manager window.  The filename ends with "zipped.exe" or "".  If you cannot find the file, you may use Search on your Windows explorer.  Search for the name of the file you downloaded.  If that fails, download again, noting carefully where you saved the file.  The file name contains "zipped" in it.

  4. Double-click on the zipped file.  This will unpack several planetary images.  When you unpack them, be sure to place them in a separate folder with the planet and year as a label.  If you don't make a separate folder, you files will be all jumbled up between different planets and years.

  5. Launch Irfanview.  This is an image viewing and rudimentary image editing program.  It is free for downloading for educational and personal use.

  6. Open one of the planet images.  Use File - Open on the main menu in Irfanview.  In the file open dialog you  should navigate to the folder containing the images you recently downloaded and unpacked.

  7. Browse through all the images by pressing the <space> or the <Page Down> key.  These images may or may not be in order, but you should see all the stars from each image appear in the same place, but the planet is in a slightly different location with each image.  If the images are not in order, you should re-name the files so that they are displayed in order from oldest to newest.  The filenames are date encoded so they should be displayed in order.
  8. Display the best image as a negative (use the Image - Negative from the main menu of Irfanview).  Important.  It is easier to track and locate stars in a negative image than the conventional positive image.  It also conserves ink and toner when printing.  Don't print yet!

  9. Annotate the image in Irfanview.  Use the mouse to drag a box on the image in one of the image corners, and insert text (Edit - Insert text into selection).  Be sure to choose a suitable font - don't use the symbol font!!.  Label the image with its date and your name.  If you don't like the annotation or the text box is not large enough, use the "undo" command and do it again!

  10. Print the image from Irfanview (File - Print).  Do not print if the image is not annotated!  Do not print unless the image is a negative (black stars on white background).  Choose landscape someplace in the printer properties to get print that is as large as possible.  Only print one image.

  11. Plot the locations of the planet on the negative print.  Be sure to use pencil so erasures are possible.  Locate the planet on the negative print by noting alignments with other stars, etc.  Place a small "+" at the correct location and label each "+" with its respective date.

  12. Label any bright stars with their common names from consulting your planisphere.  This is a good place to take a break.

Explanation and Discussion.  (You should allow about 45 minutes to complete the next exercise).   Go the the next page.  When finished with the exercise, use the "back" button to return to this page and be prepared to discuss the following questions in your report.  See the following links to help explain the apparent motion: Jupiter at opposition, and Jupiter at "quadrature".

  1. Note the direction in the sky that the planet wanders - consult the planisphere.  Please use the celestial directions (North, South, East, West), not up, down , left , right. Use the planisphere, orient the constellation on your printed sheet so that it matches the orientation on the planisphere, and mark the principal directions on the printout.

  2. All the planets orbit the sun toward the celestial east.  Is the planet's apparent motion in this direction?  Explain on the basis of the relative motion of the earth and the other planets.

  3. Explain the physical significance of the observations regarding Kepler's laws (see text).