Contains:  Solar system body or event
Io Occulting Ganymede March 29 2021, 



Io Occulting Ganymede March 29 2021

Acquisition type: Lucky imaging

Acquisition details

Date: March 29, 2021

Time: 07:06

Focal length: 2029

Transparency: 5

Resolution: 616x460

File size: 5.1 MB

Locations: Texas Home, Missouri City, Texas, United States

Data source: Backyard


The mutual eclipse season for Jupiter's four Galilean moons has begun. This morning (Mar 29, 2021) right at sunrise there was an occultation of Ganymede by Io. I used a 685IRpass filter on an ASI224MC camera attached to a C8 SCT to attempt to capture the event. I made a sequence of 18 60 sec video captures with a 60 sec interval between captures beginning at 6:52am CDT. The event began at 7:06am CDT and lasted 8 minutes. Sunrise was at 7:16am CDT so the images after the occultation were in full daylight. Additionally, Jupiter was only at 20 degrees altitude.

In the animation above, Io and Ganymede are fairly close together at the lower center of the image. Io is on the left, Ganymede on the right. Io moves to the right, passing in front of Ganymede which is moving to the left. The orbital plane of the moons is currently in line with our view from Earth which allows us to view these mutual events. This alignment occurs twice in a Jovian year (about 12 Earth years) making these eclipse seasons visible every 6 years. This season started in January of this year and runs through November. The next one will be in 2027.

I processed the 18 captures in AS!3, sharpened them in RegiStax6, manually aligned them in PS CC 2021 as well as attempted to normalize the backgrounds of the images post event. I used PIPP to create the animated GIF, which is admittedly quite rough. I apologize for Jupiter's appearance after the occultation. It was, by then, full daylight and I attempted to change settings to compensate for the increased sky brightness but apparently didn't do a very great job. This was my first attempt at this type of imaging.

Almost all of the mutual events occur in the early morning though some will be before sunrise. I hope to attempt additional events as this eclipse season progresses.



  • Io Occulting Ganymede March 29 2021, 


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    Io Occulting Ganymede March 29 2021,