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Solar Rotation Screen



Required Software

Click Filename to Download
Or Icon to Go to FTP Site,
These are self-extracting files and will install 
themselves when you run them on your computer.
  • SolarRtn.EXE -Executables and a sample of  11 image files (17 MByte), enough to give a flavor of the exercise.
  • SolarRtnV1---A January 2005 update to be loaded after installing Version 1.00 adds multiple selection of images for load, including a “Select All” menu item. The display of images during animation has been improved to eliminate “flashing” and obvious variations in radius between images from difference sites. An indicator now shows when the images are not in increasing time sequence (sorted), and a sort feature has been added.
    NOTE:  Users who have CD-ROMs containing an earlier version of the software should install them first, then install this software update. (If you are reading the images directly from the CD-ROMs without installing them on hard disk you can simply install this update and use it.)
  • TO REQUEST A COMPLETE INSTALLATION DISK WITH ALL  368  IMAGES OF THE SUN -Too large to download; will be sent by mail. Reinstall the program from this disk, and you will be able to access all the images provided on it. NEW NOVEMBER 2003: A second disk with 375 more images of the sun from 2002.  Please ask specifically for this as well.  Note: If you have the first release of the software, this disk also contains revised software that will enable you to use both sets of images and any further sets.

Student manual (Acrobat pdf format)

Student manual (MS Word 2000 format)

Questionnaires and Pre/Post-Tests 
(Acrobat pdf format)

A Description of the Lab: 

Purpose: To introduce students to the techniques that astronomers use to measure the rotation rate of the sun using images of sunspots. To introduce some of the difficulties of using two-dimensional images to derive three-dimensional properties of celestial objects.  

This exercise enables students to measure the rate of rotation of the sun at various latitudes using an archive of 368 images of the sun obtained over a four month span in 2002 obtained by the GONG project . Because of the high spatial and temporal resolution of the sample, these are the best images to date from which students can determine the solar rotation rate.   Software provided enables student to access the GONG images, display them as still images or animations, measure and record the positions of sunspots, plot its heliocentric coordinates versus time, and thus determine the apparent rotation period of the spot. A second archive of an additional 375 images spanning June to August 2002 was made available in November 2003.

A student manual provided for this exercise describes the method of analysis and the operation of the software.  It provides two possible ways of doing the exercise, a "Discovery Based" procedure which is open-ended, and a "Step by Step" procedure which leads students through the exercise, filling in tables and answer sheets as they go.

The downloadable file accessed on this page is a self-installing file which contains 11 images suitable for measurement .  It can be used to measure one or two spots, and will give a flavor of the exercise.  

The full dataset, with a self-installing program for the software and the data, is available free of charge by writing Project CLEA, Department of Physics Gettysburg College,  Gettysburg, PA 17325, (email ), or by filling in the request form accessed by the link on this page.  


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