The following animation shows the  Jovian moons Io, Ganymede and Callisto casting their shadows on Jupiter. The occurence of three sataellite shadows visible on Jupiter happens about once every 10 years (for a given location on Earth). First I show some still pictures to get you oriented, then I show a "movie."  My equipment and image analysis are described at the end.

Figure 1. This picture was made early in a 2-hour observing run on the night of March 27/28, 2004, when 3 moons were visible and only one satellite shadow falls on Jupiter. From left to upper-right the satellites are Io, Europa and Callisto. Ganymede is in front of Jupiter and can't be seen. The shadow of Callisto can already be seen near Jupiter's north pole. This image was taken at 06:05 UT, March 28, 2004. North is up (and slightly to the left).

Figure 2. Blink of image taken at 06:25 UT and a predicted satellite positions by TheSky (Ver 6.0) for this time.

Ganymede is located where the image shows a spot in the upper-left of Jupiter's disk (it's a light spot in this inverse brightness image).  I tentatively identify this spot as due to Ganymede being darker than the bright north equatorial zone.

Figure 3. About 2 hours later (08:08 UT) the satellites have moved in their orbits and now Callisto's shadow is barely visible near the top, Io's shadow is just appearing on the left edge, and Ganymede's shadow is just left of center - as indicated by the circles. Ganymede is still in front of Jupiter at the location of the dark spot north of the northern hemisphere belt; more on this below.

Figure 4. Same as above, but without the circles and larger.

Figure 5. Blink of image taken at 08:08 UT and a predicted satellite positions by TheSky (Ver 6.0) for this time.

Ganymede is again co-located with the dark spot in the northern equatorial bright zone (bright in this negative image).

Figure 6. The above 12 images were made during a 2-hour period on 2004.03.28, 05:55 to 08:10 UT. Each image underwent extensive processing to allow the satellites to be seen while not saturating the planetary disk. To see a smoothed" version of the above sequence (181 images, 650,000 bytes), click smooth.

Technical Details:

    Telescope:  14-inch, Celestron CGE-1400, aperture mask with 5-inch hole, EFL = 1934 mm
    Camera:  SBIG ST-8XE CCD with SBIG CFW and photometric red filter in use, exposure 0.3 seconds
    Location:  Hereford, AZ, elevation 4650 feet ASL
    Program for controlling hardware: MaxIm DL/CCD, MaxPoint
    Program for image processing: MaxIm DL
    Image processing: digital development low-pass with 3% cutoff, Kernel filter high-pass more, double size, Kernel filter high-pass more, Kernel median 3x3, Kernel high or Kernel more (depending on resolution)
    Observing Conditions:  Clear, warm, "atmospheric seeing" was good with FWHM = 2.5 to 2.9 "arc for 0.3-second exposures.
    Observer: Bruce L. Gary

The Sky & Telesccope web page article for this event is at S&T_Jup and Gu Yu's animation is at GuYu.  An even better animation has become available, at http://skyandtelescope.com/news/article_1241_1.asp

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This site opened:  March 28, 2004.  Last Update:  April 16, 2004