Sunday night Perth time saw a rare astronomical event – the occultation of the planet Saturn by the Moon!
An occultation is the technical term for when an object in our solar system moves in between our line of sight and another astronomical object, either in our own solar system or another star or galaxy. It comes from the word ‘occult’ which came from the Latin word ‘Occultus’ meaning to cover over or to hide.
A total solar eclipse is a special and perhaps the most well-known form of occultation many people are familiar with as the Moon’s disk hides the light of the daytime Sun from us down on Earth.
(Definitely worth viewing full size – just click once, then once again.) 🙂The relative closeness of our Moon makes it seem massive in size compared to the much more distant ringed planet, Saturn. My camera’s unique focussing and light balancing algorithms meant considerable exposure adjustment had to be done in post processing to make Saturn seem anything but a ghostly shadow.
The more eagle-eyed viewers may be able to see a star in the constellation Ophiucus half way between the Moon’s shadow and Saturn. This shot was taken at 8:33 pm local time with an approximate zoom of 80X.
The gap between the two objects narrows as the Moon appears to ‘back up’ into Saturn as the occultation was about to begin. The local time was 9:52 pm. I added the blue circle to give a better idea of how close the Moon was to blocking out the planet. The closer Saturn got to the Moon the better my camera was able to pick up the light of the planet, requiring less post-processing to see it clearly.
A Moon shot as it hides the planet from view taken at 10:30 pm. It takes about 70 minutes for the Moon to travel far enough for Saturn to be seen peering out from the opposite side to where it was covered up.
At 11 20 pm Saturn and it’s rings are now visible again as the giant Moon serenely slides on by.
To put things into their true perspective: The Moon has a diameter of approximately 3350 km (2100 miles) and is on average around 385,000 km (247,000 mi) away from us.
Saturn has a diameter of 116,000 km (70,000 mi) – 9 times our own earth – and is currently around 1.3 billion km (800,000 mi) away from us. The rings of Saturn extend out for 120,000 km (75,000 mi) either side of the planet and yet are less than 50 metres (165 ft) thick!
If Saturn were to replace the earth in it’s orbit the rings would not even reach the orbit of our Moon. Saturn is currently thought to have 62 of it’s own moons, only one of which, Titan, is larger than our own.