Sky and Telescope - December 2015 - 46

OBSERVING

Celestial Calendar

Jupiter's Moons

Moon Occults Venus in

Dec 1
2
3

EAST

WEST

4
5
6
7
8
9
10

Io

11
12
13

Europa

The waning Moon had crept right up to
Venus when Ravindra Aradhya took this
picture from Bangalore on February
26, 2014. "It was an amazing sight,"
he writes. "This photo was taken just
before the Moon fully occulted the dark
side of Venus." He used an 8-inch f/10
Schmidt-Cassegrain scope.

On December 7th, if the sky is clear,
practically everyone with a telescope or
binoculars in North and Central America
will have a chance to see the thin waning
crescent Moon cover and uncover Venus
in the daytime.
Watching this event may or may not be
easy; the deeper the blue of your sky the
better. The slim Moon will be just 13%
illuminated and about 43° west of the Sun.
If there's any haze, Venus may be the ﬁrst
thing you spot in your binoculars or ﬁnderscope. It's tiny, but it has a much greater
surface brightness to penetrate a bright sky.
Carefully sweep the area of sky about four
ﬁst-widths to the Sun's right if you're in the
East, a little above right in the Midwest,
and higher to the upper right farther west.
You're looking for a tiny white dot close to a

14
15

Morning Action at Jupiter

16
17
18

Ganymede
Callisto

19
20
21
22
23
24
25
26
27
28
29
30

December ﬁnds Jupiter rising in the
middle of the night and, ﬁnally, standing at its highest in the south around
the ﬁrst light of dawn. That's the best
time to train a telescope on its banded
globe, which enlarges this month from
36 to 39 arcseconds wide across its equator. That's smallish for Jupiter but bigger than any other planet (see page 44).
Any telescope shows Jupiter's four
big Galilean moons. Binoculars usually
show at least two or three. Identify them
using the diagram at left.
All the interactions in October
between Jupiter and its satellites and
their shadows are tabulated at right.
Here are the times, in Universal
Time, when the Great Red Spot should
cross Jupiter's central meridian. The
dates, also in UT, are in bold. (Eastern
Standard Time is UT minus 5 hours.)

31
November 1, 8:30, 18:25; 2, 4:21, 14:17; 3, 0:13,
10:08, 20:04; 4, 6:00, 15:56; 5, 1:51, 11:47, 21:43;
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.

6, 7:39, 17:34; 7, 3:30, 13:26, 23:22; 8, 9:17, 19:13;
9, 5:09, 15:05; 10, 1:00, 10:56, 20:52; 11, 6:48,
16:43; 12, 2:39, 12:35, 22:30; 13, 8:26, 18:22; 14,
4:18, 14:13; 15, 0:09, 10:05, 20:01; 16, 5:56, 15:52;

17, 1:48, 11:43, 21:39; 18, 7:35, 17:31; 19, 3:26,
13:22, 23:18; 20, 9:14, 19:09; 21, 5:05, 15:01;
22, 0:56, 10:52, 20:48; 23, 6:44, 16:39; 24, 2:35,
12:31, 22:26; 25, 8:22, 18:18; 26, 4:14, 14:09;
27, 0:05, 10:01, 19:56; 28, 5:52, 15:48; 29, 1:43,
11:39, 21:35; 30, 7:31, 17:26.
December 1, 3:22, 13:18, 23:13; 2, 9:09, 19:05; 3,
5:00, 14:56; 4, 0:52, 10:48, 20:43; 5, 6:39, 16:35;
6, 2:30, 12:26, 22:22; 7, 8:17, 18:13; 8, 4:09, 14:04;
9, 0:00, 9:56, 19:51; 10, 5:47, 15:43; 11, 1:39, 11:34,
21:30; 12, 7:26, 17:21; 13, 3:17, 13:13, 23:08; 14,
9:04, 19:00; 15, 4:55, 14:51; 16, 0:47, 10:42, 20:38;
17, 6:34, 16:29; 18, 2:25, 12:21, 22:16; 19, 8:12,
18:08; 20, 4:03, 13:59, 23:55; 21, 9:50, 19:46; 22,
5:42, 15:37; 23, 1:33, 11:29, 21:24; 24, 7:20, 17:16;
25, 3:11, 13:07, 23:03; 26, 8:58, 18:54; 27, 4:49,
14:45; 28, 0:41, 10:36, 20:32; 29, 6:28, 16:23; 30,
2:19, 12:15, 22:10; 31, 8:06, 18:02.

These times assume that the spot is
at System II longitude 230°. 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 will slightly improve
the contrast of Jupiter's reddish and
brownish markings.
Sky and Telescope - December 2015

Table of Contents for the Digital Edition of Sky and Telescope - December 2015
