Astronomical Observing and Photography - Joseph Cali


Occultation of Jupiter's moon Europa, by the shadow of Jupiter's moon, Io.

Date and Time: Monday May 10th, 2021 02:34am to 02:38am

Thanks to my friend, Phil Jones. Phil drew my attention to an interesting event coming up on May 10 at uggh 2:34 am.

Io, one of the four Galilean moons, is going to cast its shadow over another moon, Europa, in a deep partial eclipse.

This only occurs when the orbital plane of Jupiter's satellites align with the orbital plane of Jupiter's path around the Sun so that the shadows of one satellite can land on another.  Earth, by convention only, is defined as having a 0 degree inclination, all other planets are measured relative to this plane. Jupiter's plane is inclined 1.3 degrees to this. This alignment occurs about once every 6 years and even then the actual eclipse events are not guaranteed. Shadows of the planets cast on the surface of Jupiter or moons disappearing into the shadow of Jupiter are far more common.

The dimming event occurs at 2:34am on the morning of May 10 and exits the shadow and brightens at 2:38am.

Jupiter is very easy to find. At 2:30am it is due eastand approximately 30 degrees above the horizon  anywhere from Bribane to Melbourne and by far the brightest object in that part of the sky. Farther inland and west, it is about 1 degree lower for each degree of longitude you are located west of the 150 degrees east longitude meridian.

Through any small telescope, the four Galilean Moons are easily visible. On that morning, they will all be aligned above Jupiter with respect to the horizon as we see it with the naked eye. Remember that your telescope, depending upon its optical design, may invert or reverse the view. Regardless, Europa at that time is the second moon going outwards from Jupiter. 

Through a small telescope, the moons are easily visible as starlike objects. A very large amateur scope may show a very small disc.  The amateur observer will not see the shadow progression, they will only see the starlike object dim for 4 minutes prior to its exiting the shadow and brightening again.

I have seen photographs  of Jupiter taken with high quality telephoto lenses in the 200-600mm range that clearly show the 4 Galilean moons. A sequence of images stitched into a time lapse animation will record the disappearance nicely. Just make sure to determine a suitable exposure or setting by viewing images in camera then lock in that setting in manual mode so as to stop any variation from frame to frame.

Clear skies!

Kind regards

Nightscape Astrophotography & Workshops


Return to home page