Sky & Telescope - December 2021 - 50

DECEMBER 2021 OBSERVING
Celestial Calendar
Action at Jupiter
AS DECEMBER GETS UNDERWAY,
Jupiter transits the meridian roughly
half an hour after sunset and sets late
in the evening. That means, the earlier
you look, the better the telescopic views
should be. On the 1st of the month, the
gas giant shines at magnitude -2.3 and
presents a disk 38″ across.
Any telescope reveals the four big
Greatest
eclipse
Galilean moons, and binoculars usually
show at least two or three. The moons
orbit Jupiter at different rates, changing
positions along an almost straight line
from our point of view on Earth. Use
the diagram on the facing page to identify
them on any given date and time.
All the observable interactions between
Jupiter and its satellites and their shadows
are tabulated on the facing page.
Features on Jupiter appear closer to
9:00 UT
pDuring the early morning hours of December 4th, the Moon's shadow sweeps across the Southern
Ocean, South Orkney Islands, and Antarctica. Unlike most eclipses where the shadow moves
from west to east, this one will travel from east to west. Touchdown occurs about 500 kilometers
southeast of the Falkland Islands. Greatest eclipse of 1 minute 54 seconds occurs just off the
coast of Berkner Island in the Weddell Sea at 7:33 UT.
Minima of Algol
Nov.
UT
6
9
12
15
18
20
23
26
29
15:39
12:28
9:16
6:05
2:54
23:43
20:32
17:21
14:11
Dec.
2
5
8
11
13
16
19
22
25
28
31
the central meridian than to the limb
for 50 minutes before and after transiting.
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.)
November 1: 6:44, 16:39; 2: 2:35,
UT
11:00
7:49
4:38
1:27
22:16
19:05
15:54
12:44
9:33
6:22
3:11
These geocentric predictions are from the recent
heliocentric elements Min. = JD 2457360.307 +
2.867351E, where E is any integer. They were
derived by Roger W. Sinnott from 15 photoelectric
series in the AAVSO database acquired during
2015-2020 by Wolfgang Vollmann, Gerard Samolyk,
and Ivan Sergey. For a comparison-star chart
and more info, see skyandtelescope.org/algol.
50 DECEMBER 2021 * SKY & TELESCOPE
18
30
PERSEUS
38
Algol
21
29
TRIANGULUM
34
12:31, 22:27; 3: 8:22, 18:18; 4: 4:14,
14:10; 5: 0:06, 10:01, 19:57; 6: 5:53,
15:49; 7: 1:44, 11:40, 21:36; 8: 7:32,
17:27; 9: 3:23, 13:19, 23:15; 10: 9:11,
19:06; 11: 5:02, 14:58; 12: 0:54, 10:49,
20:45; 13: 6:41, 16:37; 14: 2:33, 12:28,
22:24; 15: 8:20, 18:16; 16: 4:12, 14:07;
17: 0:03, 09:59, 19:55; 18: 5:51, 15:46;
19: 1:42, 11:38, 21:34; 20: 7:30, 17:25;
21: 3:21, 13:17, 23:13; 22: 9:09, 19:04;
23: 5:00, 14:56; 24: 0:52, 10:48, 20:43;
25: 6:39, 16:35; 26: 2:31, 12:27, 22:22;
27: 8:18, 18:14; 28: 4:10, 14:06; 29:
0:02, 09:57, 19:53; 30: 5:49, 15:45
December 1: 1:44, 11:40, 21:35;
pPerseus is approaching the zenith on
chilly December evenings. Every 2.7 days,
Algol (Beta Persei) dips from its usual
magnitude 2.1 to 3.4 and back. Use this
chart to estimate its brightness in respect
to comparison stars of magnitude 2.1
(Gamma Andromedae) and 3.4 (Alpha
Trianguli).
2: 7:31, 17:27; 3: 3:23, 13:19, 23:14;
4: 9:10, 19:06; 5: 5:02, 14:58; 6: 0:54,
10:50, 20:45; 7: 6:41, 16:37; 8: 2:33,
12:29, 22:24; 9: 8:20, 18:16; 10: 4:12,
14:08; 11: 0:04, 09:59, 19:55; 12: 5:51,
15:47; 13: 1:43, 11:39, 21:34; 14: 7:30,
17:26; 15: 3:22, 13:18, 23:13; 16: 9:10,
19:05; 17: 5:01, 14:57; 18: 0:53, 10:49,
20:44; 19: 6:40, 16:36; 20: 2:32, 12:28,
22:24; 21: 8:20, 18:15; 22: 4:11, 14:07;
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http://www.skyandtelescope.org/algol
Sky & Telescope - December 2021

Table of Contents for the Digital Edition of Sky & Telescope - December 2021
