Steve’s Virtual Planet

SVC Tip #2 - Tracking Jupiter moon occulations

As already mentioned on the SVC Tip #1, one of my favorite internet tools is Sky View Cafe.  This tool is very useful for determining the location and position of the moons of Jupiter.

I’ve used the special tab called “Moon/GRS” a number of times in the last few months to document the Galilean moons and to plan my viewing. For my outreach work, I also produce a printout with the orientation of the view set to match the scope being used.

For the evening of November 8, 2010, I had noticed that Europa and Io were going to be ducking out of sight right before the beginning of my planned GRS observation. By “walking” the time setting back and forth, I could determine to the minute when the moons would slide behind Jupiter. So, I made sure I was completely setup and alligned on the planet about 10 minutes before hand. And sure enough, right on cue, Europa slid out of view at 18:19, followed by Io a while later at 18:51. You can see it work for real just by setting the clock back to Nov 8, 2010, 18:00 hours and slowly running the clock forward.

Another useful thing you can do with SVC is get a table of the exact values for these events. Use the “Tables” tab and select “Galilean Moons/GRS” from the first button. Leave the next button set for “One Day”, then click the right hand button “Generate Table”. The example text is shown below.

Galilean moon events (US/Eastern time zone)
GRS transits based on tabular GRS longitudes from 1969-04-01 to 2010-10-01
Interpolated GRS longitude at 2010-11-08 18:00 is 157.5°

2010-11-08 18:19   II. Oc.D.
18:51    I. Oc.D.
19:08  GRS transit
22:09    I. Ec.R.
23:19   II. Ec.R.
2010-11-09 05:03  GRS transit
14:59  GRS transit
16:04    I. Tr.I.
17:10    I. Sh.I.