Thursday, December 27, 2012

Double Shadow Transit on Jupiter - 28 Dec 2012

Weather permitting, we may see a rare sight on Jupiter - double shadow transits. Jupiter's moons Io and Ganymede will be casting their shadow on Jupiter at the same time.

This event will occur at about 36 mins past midnight tonight.

These two shadows visible tonight from Singapore are going to appear at the same time on Jupiter only for about 3 or 4 mins. Ganymede's shadow is transiting out of Jupiter, while Io's shadow just started its transit across Jupiter.

Visually, this will be good test of your telescope's optics and your vision. So start observing early at least a couple of minutes before 00:36am. This is also a good opportunity for astrophotographers to capture this rare sight.

While waiting for this double shadow transit to happen, you can enjoy watching Ganymede's shadow drifting across Jupiter. And after the double, Io's shadow drifting across it.

Here are the timings:

Ganymede Shadow Transit  = 10:39 pm (27 Dec) -- 00:49 am (28 Dec)
Io's Shadow Transit = 00:33 am (28 Dec) -- 02:44 am (28 Dec)


Early in the evening, Jupiter's Great Red Spot (GRS) will be visible in the centre of the planet at about 7.20pm. So you can start observing the moment you see a bright "star" (Jupiter) in the East at about 30 degrees above the horizon - about 3 fists high on your extended arm.

Another way to spot Jupiter tonight is to use Moon as a guide. Look at the brightest "star" above Moon.

A single shadow transit on Jupiter is quite common. A double is rare. A triple is very very rare. Added bonus will be Jupiter's GRS also visible when such shadow transits occur.

There should be another spectacular double shadow transit visible in Singapore in early January 2013. But the timing is less convenient and Jupiter's position is nearer to the horizon. Will blog or tweet about it in the future.

So wishing all of us good luck and clear skies tonight!

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