February 19, 2019

AstroEvent for the week of June 30th-July 7th, 2008.

And now for a difficult challenge…

I give you a New England Occultation.

First up, I’d like to apologize for the short notice on this week’s featured event, which occurs seconds before midnight tonight June 30th over New England and the Canadian Maritimes. A 10th magnitude star in the constellation Boötes will be occulted by the 12th magnitude asteroid Aquitania for a duration of up to seven seconds. The path crosses from north to south, through Newfoundland, Quebec, skirting the New Hampshire Maine border and Vermont, then on through Massachusetts and Connecticut and over Long Island before passing out to sea in the Atlantic. A link for finder charts and technical info can be found at this site. Occultations can be difficult to observe; familiarize yourself with the star field prior to attempting to spot the event. The International Occultation Timing Association seeks accurate timings of this and other occultation events. If enough timings can be gathered, a rough outline of the asteroid can be inferred. Some amateurs choose to video the event, but visual timed sightings can also prove useful. The star should blink-in and blink-out in an abrupt fashion. At the 10th magnitude, the star is on the verge of binocular resolution; a wide field telescope would prove more practical. Even if you are outside of the path, (such as myself in Northern Maine!) It may still be worth a look; there is an uncertainty factor involved with most occultation paths. See multiple blinks? The asteroid may have a tiny, undiscovered companion satellite! Amateurs have discovered “asteroid moons” in the past.

Finally, don’t be discouraged. These are tough events to observe. In half a dozen events, I have yet to see a “positive”…most occultation chasers will tell you the same. Negative sightings still can provide valuable data. Clouds, equipment, faint star fields, and path shifts can all conspire against the observer. Happy occultation hunting!

This week’s astro-word of the week is Occultation. This is simply the passage of one astronomical body in front of another, the intersecting body blocking or “occulting” the light of the farther object. This is most common when the moon passes in front of a star or a planet; it can also refer to an asteroid passing in front of a star (see above) or a planet passing in front of a star. A search for ”occultation” on Youtube will return several cool videos! It is also a term used to describe eclipsing variables, when one binary star passes through our line of sight, causing a dip in magnitude. On any given month, several asteroid occultations may happen near your geographic location; however, until the 1990′s and the advent of powerful computing methods, only about half a dozen had ever been reliably observed!


  1. [...] This post was mentioned on Twitter by David Dickinson, Andrew R Brown. Andrew R Brown said: RT @Astroguyz: #AWOD: Occultation. http://bit.ly/9KQRGR In a sentence; "An Occultation of Ceres by the Moon occurs for central Asia Fri!" [...]

  2. [...] occultation occurs when one object passes in front of another as seen from the observer’s vantage point. The [...]

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