Skip to content

Jupiter Season 2021 Begins

2021 July 1
by Russ

09:31:47 UT

10:08:07 UT

10:30:19 UT

The Jupiter observing season for 2021 began for me in the pre-dawn early morning of June 19th.

When I finally landed Jupiter on the camera’s imaging chip and brought the view into focus, I was pleasantly surprised to see that the Great Red Spot was visible and, as an added bonus, a shadow transit by Jupiter’s moon Ganymede was in progress.

The first image (top left) shows the black dot of Ganymede’s shadow already having transited across two-thirds of Jupiter’s disc when I started imaging. Ganymede itself is just outside the field of view to the left.

In the second image (middle left), taken a little over thirty minutes later, Ganymede’s shadow has moved close to Jupiter’s limb, and Ganymede is just entering the field of view along the upper left edge of the image. At this point, with the transit nearing its end, Ganymede’s shadow is no longer a round dot, but appears as an elongated egg shape. This is because the shadow is no longer being cast on Jupiter’s relatively flat disc, but instead is being cast on the curved edge of Jupiter’s limb.

In the final image (bottom left), captured an hour after the first, Ganymede has moved further into the image but its shadow has now slipped off Jupiter’s face, being cast into empty space. The transit is now over.   

The seeing conditions during this session were mostly poor, but occasionally rose to fair/average. Luckily, I captured some video sequences during these brief periods of improved seeing and was able to cull enough good frames from each video to create these images.


Date: June 19, 2021
Telescope: Celestron C8 (203mm F10) and Orion Shorty 2x Barlow
Camera: ZWO ASI224MC
Captured in FireCapture. Aligned and stacked in AutoStakkert. Wavelets and color balance in Registax. Color levels, unsharp mask, crop, in GIMP.

[1] 09:31:47 UT 1800/5317 frames,  48fps,  13.91 ms.
[2] 10:08:07 UT  2000/5407 frames, 56 fps, 11.45 ms.
[3] 10:30:19 UT  2000/5595  frames, 97 fps, 10.22 ms.


No comments yet

Leave a Reply

You must be logged in to post a comment.