Occultation Introduction - Aldebaran Feb. 5, Mar. 4
Joan and David Dunham (dunham@erols.com)
Tue, 03 Feb 1998 10:24:51 -0500
Naked-eye occultations of Aldebaran
1. Thursday pm, Feb. 5, southern Europe, s.w.Asia, n. Africa
2. Evening of March 4, eastern USA, Caribbean area
Observing dynamic events that occur well above geosynchronous
orbit - an invitation to join IOTA's occultation distribution.
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Both of these occultations occur with the Moon near first
quarter phase, with the disappearance on the dark side easily
visible with the naked eye (and, more important, can be timed
accurately by anyone just with a camcorder, no telescope needed) in
the regions mentioned where the occultation will occur after sunset
(the March 4th event occurs before sunset in Mexico and the USA west
of the Mississippi River). A spectacular grazing occultation, where
multiple disappearances of the star in rapid succession might occur,
will be visible in a zone about 2 km wide near the northern limit of
the region of visibility of the occultations, which are over
northern Spain, southern France, the Swiss-Italian border (Alps),
southern Austria, Hungarian-Slovakian border, and Ukraine on Feb. 5,
and across the northeastern USA in March. Region-of-visibility
maps, predictions for many cities, and details of the northern limit
(for Feb. 5; data for March will appear later) can be found on
IOTA's Web site at
http://www.sky.net/~robinson/iotandx.htm
In general, occultation observations are valuable for measuring the
lunar profile to more accuracy than Clementine could (this
information in turn is needed to analyze total solar eclipse
timings, from which small variations of the solar diameter can be
determined), discovering close double stars that could not be
resolved by Hiparcos or other means, and for determining the sizes
and shapes of asteroids.
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This will serve as an introduction. The above site also has
links to other occultation sites, especially for asteroidal
occultations (those in Europe should visit the European Asteroidal
Occultation Network, EAON, site). Like artificial satellite passes,
you might appreciate the dynamism of these occultations, most of
which need at least a small telescope. Also like artificial
satellites, the paths for asteroidal occultations often can't be
predicted reliably until a few days before. If you would like to be
actively notified of such events and are not already on my
distribution, please send me your coordinates and telescope
information, and we can supply local occultation predictions and
messages with updated path and expedition information. The Seesat
mailing list is not appropriate for use for most occultation events,
so it would be better to get on the IOTA list to receive our
information. I will only use the SeeSat list for occultations once
or twice a year before some important event visible from North
America and/or Europe, perhaps next for the good Aldebaran
occultation of Sept. 12, to reach new SeeSat subscribers and remind
the others of our important work.
David W. Dunham, International Occultation Timing Association
e-mail dunham@erols.com 1998 February 3