Sky and Telescope - October 2016 - 48

OBSERVING

Celestial Calendar

Moon, Aldebaran Meet Again
This time, a grazing occultation crosses Los Angeles and Denver.
Occu
Oc
Occultation
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atiio
ion of Aldebaran
ion
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Oct.
t 18
18 -19,
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az

Lin

Minneapolis
Sioux
Falls

No Occultation
No
Occ
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o

S&T: LEAH TISCIONE / DATA: IOTA

Denver

Los
Angeles

Las
Vegas

Occultation
visible

Most people in North and Central America are positioned for the Moon's October 18-19 coverup
of Aldebaran. It happens in a dark sky late at night. Maps of the graze line with street-level precision are in the webpage for this event at the end of the article.

Have you caught any occultation of
Aldebaran yet in the current series?
They're happening every 27 or 28 days,
once per lunar month. But most occur for
parts of the world where you are not, or in
the daytime, or with the Moon too close
to the Sun. And then, when everything
comes together right, it's often cloudy.
Skywatchers in much of North
America have their next chance late on
the night of October 18-19. The waning
gibbous Moon (86% sunlit) will cross
Aldebaran after midnight for the East, in
late evening for the Southwest. The map
above shows the area of visibility. Aldebaran will disappear on the Moon's bright
limb, for which you'll need a telescope
at high power, then will reappear from
behind the Moon's invisible dark limb up
to an hour or more later. For the reappearance, binoculars may be enough.
Here are some times:
Halifax, disappearance 3:06 a.m., reappearance 4:08 a.m. ADT; New York, d. 1:44
48

October 2016 sky & telescope

a.m., r. 2:50 a.m. EDT; Washington, DC, d.
1:36 a.m., r. 2:44 a.m. EDT; Atlanta, d. 1:18
a.m., r. 2:27 a.m. EDT; Miami, d. 1:11 a.m.,
r. 2:26 a.m. EDT; Toronto, d. 1:48 a.m., r.
2:37 a.m. EDT; Chicago, d: 12:37 a.m., r.
1:20 a.m. CDT; Kansas City, d: 12:28 a.m.,
r. 1:08 a.m. CDT; Austin, d: 12:03 a.m., r.
1:03 a.m. CDT; Phoenix, d: 11:13 a.m., r.
11:42 a.m. MDT; San Diego, d: 10:14 p.m.,
r. 10:36 p.m. PDT.
Times and other info are listed for 1,000
locations in the predictions link below.

A Populated Graze Line
The most interesting place to be will be
in a strip a few hundred yards wide along
the graze line, as told in the August issue

(page 50) for the event that happened on
July 29th. This time the graze happens
500 miles farther north. It runs right
across Los Angeles and Denver, about 50
miles southeast of Las Vegas, and about
30 miles southeast of Minneapolis. The
narrow graze zone is plotted to streetlevel accuracy (along with how to correct
for your elevation) on the special webpage
set up or this event at the link below.
Along that line, you'll probably see
Aldebaran disappear and reappear several
times in the darkness just barely oﬀ the
Moon's dazzlingly sunlit north polar
region. Most of these events will not be
instantaneous, as hills and valleys on
the Moon's northern limb slide across
the face of the giant star. Aldebaran is 20
milliarcseconds wide, or 40 meters at the
Moon's distance.
The graze "could be an interesting
opportunity for public outreach," notes
David Dunham of the International
Occultation Timing Association, "a rare
astronomical phenomenon visible with
binoculars by thousands of people who
live in the graze zone. In spite of the
bright Moon, this is one of the better
Aldebaran events in the current series for
populous parts of North America."
Enjoy these events while you can.
We're halfway through the current series;
it began on January 29, 2015, and ends on
September 3, 2018. After that the Moon
will occult no 1st-magnitude star until
2023 (Antares, on August 25th of that
year), and the next Aldebaran series won't
start until 2033.

FOR MORE INFORMATION

IOTA has set up a special web page
for the October 18-19 graze, with maps,
predicted lunar-limb proﬁles, and
other information, at occultations.org/
Aldebaran/2016October.

Detailed predictions for Aldebaran and
the Hyades star 71 Tauri, along with the
Moon's altitude, are listed for 1,000 cities
and towns at lunar-occultations.com/
iota/bstar/bstar.htm.

http://www.occultations.org/aldebaran/2016october http://www.lunar-occultations.com/iota/bstar/bstar.htm http://www.occultations.org/aldebaran/2016october http://www.lunar-occultations.com/iota/bstar/bstar.htm

Sky and Telescope - October 2016

Table of Contents for the Digital Edition of Sky and Telescope - October 2016