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Galileo's Sunspot Drawings

In 1612 during the summer months, Galileo made a series of sunspot observations which were published in Istoria e Dimostrazioni Intorno Alle Macchie Solari e Loro Accidenti Rome (History and Demonstrations Concerning Sunspots and their Properties, published 1613). Because these observations were made at appoximately the same time of day, the motion of the spots across the Sun can easily be seen. To illustrate this, thirty-six of Galileo's sunspot drawings have been placed in sequence as "flip-book" type animation which can be played at two different speeds. The faster animination better demonstates to movement of the sunspots. The slower animation affords the opportunity for more careful study of Galileo's drawings. The images are taken, with permission, from Professor Owen Gingerich's copy of the first edition of Istoria e Dimostrazioni.


Several file formats are available for making computer animations--each with its own advantages and disadvantages. Because of this, the animations of Galileo's sunspot drawings are provided in two different file formats. The MPEG format is compressed, t hus the files are small and load quickly. However, image quality is only moderate. The QuickTime format is non-comprerssed, thus the files are quite large and take a great deal of time to load. Nevertheless, the quality of the QuickTime animations is o utstanding.

MPEG Animations:
Smaller file size, but lower quality images.
Slower Animation -- 0.5 images/frame (0.70 MB)
Faster Animation -- 1.0 images/frame (0.30 MB)

QuickTime Animations:
Larger file size, but extremely high quality images.
Slower Animation -- 0.7 frames/second (4.15 MB)
Faster Animation -- 1.5 frames/second (4.15 MB)

Individual Sunspot Drawings

These are the individual images of Galileo's sunspot observations. All of these are high-resolution images.

First row (left to right):

Second row:

Third row:

Fourth row:

Fifth row:

Sixth row:

1995 Al Van Helden
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