(Posted 20 April 2018). Jupiter and one of it’s largest moons Io will put on a triple show tonight. Two of these events (the Great Red Spot transiting Jupiter and the shadow of Io falling on the cloud tops of Jupiter) will be visible in a decent sized amateur telescope. The third (Io passing in front of Jupiter) will be difficult to view in the same telescope.
Firstly, if you don’t have a telescope, you can still see Jupiter. It is the bright star visible above the Eastern horizon once the sky is totally dark. For the Gold Coast, Jupiter rises at 6.27 pm AEST. Rise times for other Australian locations can be found here.
And if you have a reasonable amateur sized telescope (I succeeded with the first two events with my 8 inch Dobsonian mounted telescope), point it at Jupiter first at 8.36 pm AEST. That is when Jupiter’s Great Red Spot transits the disc of Jupiter. Based on my last experience looking at the Great Red Spot, it was a pale salmon colour.
The shadow of Io falls onto the cloud tops of Jupiter at 8.12 pm AEST and then moves off at 10.21 pm AEST. Expect to look for something very tiny but definitely viewable.
Finally, the third event visible tonight is one I haven’t succeeded in viewing. Io itself will move across the face of Jupiter between 8.39 pm AEST and 10.47 pm AEST. Locating Io in front of Jupiter is challenging because of contrast issues. My telescope has a very large secondary mirror meaning it performs badly in this area. I wish you luck with this third challenge.
