52 March 2014 sky & telescope3 EAST WEST5791113151719212325272924681012141618202224262830
31EuropaGanymedeIoCallistoMar 1Jupiter’s Moons
OBSERVING
Celestial CalendarThe wavy lines represent Jupiter’s four big satellites. The central
vertical band is Jupiter itself. Each gray or black horizontal band is
one day, from 0h (upper edge of band) to 24h UT (GMT). UT dates
are at left. Slide a paper’s edge down to your date and time, and
read across to see the satellites’ positions east or west of Jupiter.In March Jupiter shrinks from 42′′ to 38′′
across its equator. But it’s still at its very
highest, almost overhead, around the
end of twilight when the atmospheric
seeing can be especially good. In the fol-
lowing months Jupiter will continue to
shrink, as Earth pulls farther away from
it in our faster orbit around the Sun, and
it will begin to lose altitude westward.
Any telescope shows Jupiter’s four
big Galilean moons. Binoculars usually
show two or three of them, and occa-
sionally all four. Identify them with the
diagram at left.
The table on the facing page lists all
of the interactions in March between
Jupiter, its shadow, and the satellites
and their shadows. A 3-inch telescope is
often enough for watching these inter-
esting events.
Here are the times, in Universal
Time, when Jupiter’s Great Red Spot
— currently a relatively strong shade of
orange — should cross Jupiter’s central
meridian, the line down the center of
the disk from pole to pole. The dates,
also in UT, are in bold:
February 1, 8:57, 18:53; 2, 4:48, 14:44;
3, 0:40, 10:35, 20:31; 4, 6:26, 16:22; 5, 2:18,
12:13, 22:09; 6, 8:05, 18:00; 7, 3:56, 13:52,Action at Jupiter
23:47; 8, 9:43, 19:39; 9, 5:34, 15:30; 10, 1:26,
11:21, 21:17; 11, 7:13, 17:08; 12, 3:04, 13:00,
22:55; 13, 8:51, 18:47; 14, 4:42, 14:38; 15, 0:34,
10:29, 20:25; 16, 6:21, 16:16; 17, 2:12, 12:08,
22:03; 18, 7:59, 17:55; 19, 3:50, 13:46, 23:42;
20, 9:37, 19:33; 21, 5:29, 15:25; 22, 1:20, 11:16,
21:12; 23, 7:07, 17:03; 24, 2:59, 12:54, 22:50;
25, 8:46, 18:42; 26, 4:37, 14:33; 27, 0:29, 10:24,
20:20; 28, 6:16, 16:11.
March 1, 2:09, 12:05, 22:00; 2, 7:56, 17:52;
3, 3:47, 13:43, 23:39; 4, 9:35, 19:30; 5, 5:26, 15:22;
6, 1:18, 11:13, 21:09; 7, 7:05, 17:00; 8, 2:56, 12:52,
22:48; 9, 8:43, 18:39; 10, 4:35, 14:31; 11, 0:26,
10:22, 20:18; 12, 6:14, 16:09; 13, 2:05, 12:01,
21:57; 14, 7:52, 17:48; 15, 3:44, 13:40, 23:35; 16,
9:31, 19:27; 17, 5:23, 15:18; 18, 1:14, 11:10, 21:06;
19, 7:01, 16:57; 20, 2:53, 12:49, 22:44; 21, 8:40,
18:36; 22, 4:32, 14:27; 23, 0:23, 10:19, 20:15;Christopher Go took this fi ne
image of Jupiter on December
11th with a Celestron-14 scope
from his balcony in Cebu City,
the Philippines. South is up.
Europa is visible on the right
end of the Great Red Spot.
More obvious is Europa’s black
shadow, being cast toward
celestial west (“preceding”)
because Jupiter had not yet
reached its January 5th opposi-
tion. Now Jupiter’s moons
cast their shadows eastward
(“following”). The System II
longitude at the time of this
picture was 199°; the Red Spot
was just about to transit.LUNAR O CCULTATION
On the night of March 10–11, tele-
scope users across the U.S. and
Canada can watch the dark limb of
the waxing gibbous Moon occult
the magnitude-3.6 star Lambda
Geminorum. Find the times for
your location at lunar-occultations
.com/iota/bstar/bstar.htm.CC layout.indd 52 12/23/13 11:35 AM