September 5, 2010: Jupiter Rotation

Jupiter's rotation, taking into account its big size (more than 10 times bigger than Earth) is surprisingly high. Concretely it completes a whole rotation every 9 hours and 50 minutes (approximately). That means that in a complete night observation session one could see all its surface.

Moreover, we could take a picture of it every few minutes and use them to produce a video of its rotation. Last week we travelled to Olvera, a nice town in the Cádiz mountains (south of Spain) and we carried our equipment with us to try to record the rotation of the giant planet.

The night was not specially good. According to the seeing scale proposed by Damian Peach we mainly had poor conditions but in some moments they improved to fair conditions. In previous takes we obtained better takes of the planet, as you can check it in the real video clip at the bottom of this page. We could not record all the night long and, in fact, we started our recordings after 1 AM.

However, we could record a 2 minutes long video of the planet every 5 minutes during 4 complete hours. Thus, we have 48 videos of 2000 frames (approx.) and about 1 Gb of data per video. During the following days we have processed each one of the videos and prepared the final animation. The result can be seen below at different scales (it may take some time to load):

We have processed the videos with Registax 5.1 to stack the frames and the first wavelets, Image Plus for additional sharpening, detail extraction and frame alignment and ImageMagick (under GNU/Linux) with some home-made scripts for the last adjustments and creation of the animation.

During the capture and processing of the images we have learned a few important things: 

• We have to be very careful with the dust spots in the CCD. In our video there are some of them which are quite noticeable. In a single image is possible that the spots are hidden in the planet texture but in the animation they can be easily identified as artifacts.
• 2 minutes per video may be too much for our focal length. Probably we have suffered the effects of Jupiter's rotation and lost some fine details.
• The animation would be more fluid with a picture every 3 minutes.
• Seeing changes drastically during the night and in a matter of minutes. Thus, the processing of each frame cannot be done automatically (but we have tried to automatize it the most). We have spent more than 15 hours to obtain the final video (more than 45 Gb and 100000 frames processed).
• It is quite interesting to have someone to talk to during the night to avoid getting asleep and loosing some of the photos :-)

We hope this next winter to be able to record a complete rotation of the planet.

Real video clip taken for the 18th frame of the animation. This was the best seeing we had that night.