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The moon to occult Saturn tomorrow! May 21, 2007

Posted by dorigo in astronomy, internet, news, personal, science.

…And I will be in the wrong side of the globe, darn it.

This rare and very entertaining celestial event will take place for observers in Europe and western Asia in the evening of May 22nd. The waxing crescent moon will glide over the planet at 19.11, 19.39, 19.18, 19.30, 19.27 UT for observers in London, Madrid, Paris, Milano, Moscow respectively. The reappearance from the sunlit side will occur at 20.17, 20.26, 20.24, 20.36, 20.22 UT as seen from the five cities mentioned above. Observers in eastern and southern Europe will be better placed to observe the event, because the Sun may have already set for them.

Lunar occultations of planets have fascinated me from my childhood. I first read about future forecasts of these events on an issue of Sky and Telescope I had borrowed from the Venetian amateur astronomers association (AAV). I must have been 12 years old or so, and I did not know much English back then… I still remember getting stuck with a jargon american word, “ballpark”. The sentence ran like “observers in Asia and Indonesia will be able to observe the occultation of Saturn with the moon high in the sky, and Venus and Jupiter in the ballpark”, or something like that. No mention of the word on any of my dictionaries. It sucked because I wanted to translate the article to bring it to school.

Anyway, what to expect tomorrow, if you are lucky enough to be located or to have traveled to the right region of the globe? Well, it depends on the instrument with which you will be able to observe the event. A pair of binoculars will suffice to follow Saturn disappearing and reappearing in twilight or after sunset, but where the Sun is still above the horizon you will need an instrument with some more magnification and as large a diameter as possible. If you want to know what you could see from a large instrument (say a 14″ or larger) check the picture below, taken on a twin event on March 2nd this year by Pete Lawrence in West Sussex, England:

If you want exact ingress and egress times from your location your best bet is IOTA’s site, while a collection of other images from the March 2nd event is available from the PopAstro site .

As for me, I am green with envy, but I will keep patient. On June 18th I plan to make time and telescope ready for the daylight occultation of Venus by a thin crescent, just after noon! Even though Venus is slightly less fancy to observe in a telescope than Saturn, the simple fact of being able to just search for the moon with unaided eyes and then locate the close-by Venus in plain daylight will be a treat! In fact, Venus is now at -4.5 magnitude, and it is quite easy to see in daylight, but we usually are unable to locate it because our eyes cannot focus on it unless we are aiming our view at it dead-on.

Update: just a thought: It would be so cool to observe this event from Saturn! The Earth from Saturn is probably no more than a magnitude-4 star, and the moon is one magnitude dimmer; but with a telescope, seeing the Moon’s crescent slide over the Earth’s crescent must be spectacular, especially since the Earth’s atmosphere should probably create some interesting effects. I hope the Cassini camera will catch a view of the event!



1. Kea - May 21, 2007

Great shot!! You’re going to be in South America?

2. dorigo - May 22, 2007

South America ? South America ? (frantically looking for IOTA’s site)…

Whew, no Kea, Venus will be seen disappearing behind the moon from good ole Europe this time, check it out in

Or were you referring to something else ?


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