Sky and Telescope - May 2016 - 50

OBSERVING

Celestial Calendar

Jupiter's Moons

Daily Jupiter Events

May 1

Jupiter's Great
Red Spot is
living up to its
name better than
at any time in
memory. In a
small telescope,
it's much less difﬁcult to see now.
Christopher Go
shot this stackedvideo image on
January 4th using
a 14-inch scope.
South is up.

2
3

EAST

WEST

4
5
6
7
8

Io

9
10

Europa

CHRISTOPHER GO

11
12
13
14
15

Ganymede

16
17
18
19
20
21
22
23
24

Callisto

25
26
27
28
29
30
31

The 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.

50

May 2016 sky & telescope

Telescope users in May should plan
to catch Jupiter right around the end
of twilight, while it's still high on the
meridian or just past it.
Jupiter's four big Galilean moons are
visible in any scope. Binoculars usually
show at least two or three. Identify
them using the diagram at left.
All of May's interactions between
Jupiter and its satellites and their shadows are listed on the facing page. On
Friday night May 6-7, North Americans
can watch a double shadow transit: both
Callisto and Io are casting their tiny
black shadows onto Jupiter from 4:39 to
5:42 May 7th UT. (To get Eastern Daylight Time, subtract 4 hours from UT.)
And here are all the times, in Universal Time, when Jupiter's Great Red
Spot - unusually vivid this year! -
should cross the planet's central meridian. The dates, also in UT, are in bold.
April 1, 3:56, 13:51, 23:47; 2, 9:42, 19:38; 3,
5:34, 15:29; 4, 1:25, 11:21, 21:16; 5, 7:12, 17:08;
6, 3:03, 12:59, 22:54; 7, 8:50, 18:46; 8, 4:41,
14:37; 9, 0:33, 10:28, 20:24; 10, 6:20, 16:15;
11, 2:11, 12:07, 22:02; 12, 7:58, 17:54; 13, 3:49,
13:45, 23:41; 14, 9:36, 19:32; 15, 5:28, 15:23;
16, 1:19, 11:15, 21:10; 17, 7:06, 17:02; 18, 2:57,
12:53, 22:49; 19, 8:44, 18:40; 20, 4:36, 14:31;
21, 0:27, 10:23, 20:18; 22, 6:14, 16:10; 23, 2:05,

12:01, 21:57; 24, 7:52, 17:48; 25, 3:44, 13:39,
23:35; 26, 9:31, 19:27; 27, 5:22, 15:18; 28,
1:14, 11:09, 21:05; 29, 7:01, 16:56; 30, 2:52,
12:48, 22:44.
May 1, 8:39, 18:35; 2, 4:31, 14:26; 3, 0:22,
10:18, 20:14; 4, 6:09, 16:05; 5, 2:01, 11:56,
21:52; 6, 7:48, 17:44; 7, 3:39, 13:35, 23:31; 8,
9:26, 19:22; 9, 5:18, 15:14; 10, 1:09, 11:05,
21:01; 11, 6:57, 16:52; 12, 2:48, 12:44, 22:39;
13, 8:35, 18:31; 14, 4:27, 14:22; 15, 0:18, 10:14,
20:10; 16, 6:05, 16:01; 17, 1:57, 11:53, 21:48;
18, 7:44, 17:40; 19, 3:36, 13:31, 23:27; 20,
9:23, 19:19; 21, 5:14, 15:10; 22, 1:06, 11:02,
20:57; 23, 6:53, 16:49; 24, 2:45, 12:40, 22:36;
25, 8:32, 18:28; 26, 4:23, 14:19; 27, 0:15,
10:11, 20:07; 28, 6:02, 15:58; 29, 1:54, 11:50,
21:45; 30, 7:41, 17:37; 31, 3:33, 13:29, 23:24.

These times assume that the Great
Red Spot is centered at System II longitude 234°. It will transit 12/3 minutes
earlier for each degree less than 234°,
and 12/3 minutes later for each degree
greater than 234°. Features on Jupiter
appear closer to the central meridian
than to the limb for 50 minutes before
and after transiting.
A light blue or green ﬁlter slightly
increases the contrast and visibility of
Jupiter's reddish and brownish markings. An orange ﬁlter helps to darken
the blues.
Sky and Telescope - May 2016

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