Observations

Titan shadow observed at Sydney Observatory on 12 March 2009

Saturn imaged during the Titan transit

Saturn imaged during the Titan transit. A hint of Titan’s shadow is visible in the blow-up version of the image (below) at the left “nine o’clock” position. Image taken afocally (camera held to the eyepiece) through Sydney Observatory’s 40-cm Meade telescope by Ross Mitchell.

Last evening (12 March 2009) Saturn’s giant moon Titan crossed in front of the north edge of the planet casting a shadow as it did so. This rare event was viewed by an excited group of visitors through a number of telescopes at Sydney Observatory including the large 40-cm computer-controlled reflecting telescope in the north dome.

A larger scale version of the image of Saturn shown above. A hint of Titan's shadow is visible at the left "nine o'clock" position. Image taken afocally (camera held to the eyepiece) through Sydney Observatory's 40-cm Meade telescope by Ross Mitchell.

A larger scale version of the image of Saturn shown above. A hint of Titan’s shadow is visible at the left “nine o’clock” position. Image taken afocally (camera held to the eyepiece) through Sydney Observatory’s 40-cm Meade telescope by Ross Mitchell.

Threatening clouds parted for the occasion and Saturn could be viewed with only occasional thin clouds disrupting the view. Before the event my Observatory colleagues and myself were unsure how difficult it would be to see Titan and its shadow against the bright disc of the planet. As the evening progressed and Saturn rose higher in the sky the shadow became more obvious. Most visitors who were viewing at the time were satisfied that they had glimpsed the shadow at the planet’s northern edge. Titan itself was probably a little too elusive.

Observatory guide Gemma adjusts the 40-cm Meade telescope in Sydney Observatory's north dome. Image Ross Mitchell.

Observatory guide Gemma adjusts the 40-cm Meade telescope in Sydney Observatory’s north dome. Image Ross Mitchell.

The evening began with yours truly explaining some of the details of the transit. Using a little mocked-up model of Saturn, I demonstrated how during Saturn’s 29-year period around the Sun there are two times about 14 years apart when the rings are edge-on to the Earth. This year is one of those occasions and this is the only time that Titan can appear to cross in front of Saturn.

The evening continued with a viewing of an Iridium flare, as fortuitously there was a bright one predicted at 8:27:34 pm. A colleague and myself picked up the satellite early and used green lasers to point it out to the visitors. Seeing a faint point of light blossom out into a bright flare was an awesome experience both for first time viewers and to regulars.

Afterwards Saturn observing began in earnest. With the pleasant weather, the view of the famous planet with its rings stretched into almost into a straight line and the glimpse of Titan’s shadow, visitors and staff alike enjoyed a memorable evening. Stay tuned for more exciting International Year of Astronomy events at Sydney Observatory during the rest of 2009!

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