Sky and Telescope - December 2017 - 49

The Moon
Occults Aldebaran

Geminid Meteor Shower
Dec 13, 9 pm

GEMINI

Radiant
LY N X

Castor
Pollux

CANIS
MINOR

Procyon

10°

Looking East

G REGG DINDER M A N / S&T

p This should be a good year for the Geminids.
There's almost no moonlight to interfere with
observing, and the shower reliably produces
a high meteor count. To determine if a meteor
is a Geminid, trace its path backward. If you
end up at a point close to Castor, you've got
yourself a winner.

it in peak activity), but it's extremely
unlikely you'll see that many. You don't
have to be particularly lucky to see
a few Geminids if you spend even a
half hour outside, however. And don't
be surprised if you see a stray meteor
whose origin can't be traced back to
the Geminids' radiant point. It may be
a sporadic, or it may come from one of
the several proximately timed minor
annual showers, like the Monocerotids
or the Sigma Hydrids.
Geminid visibility isn't great for the
Southern Hemisphere, since the radiant
never climbs above the horizon, but
southern observers may still see 10-20
meteors in an hour.

Minima of Algol
Nov.

UT

Dec.

UT

2

10:18

1

2:27

5

7:07

3

23:16

8

3:56

6

20:05

11

0:45

9

16:55

13

21:34

12

13:44

16

18:22

15

10:33

19

15:11

18

7:22

22

12:00

21

4:11

25

8:49

24

1:00

28

5:38

26

21:49

These geocentric predictions are from the
recent heliocentric elements Min. = JD
2445641.554+ 2.867324E, where E is any
integer. For a comparison-star chart and
more info, see skyandtelescope.com/algol.

ON SUNDAY MORNING December 3rd
for North America, the full Moon occults the
brightest star in its path, Aldebaran. Only those
in the far northwest of North America or in Asia
will be able to catch this one, and they will be
challenged by a beaming Moon and a rising
Sun. Seattleites might see the star slip behind
the Moon about 70 minutes before moonset,
but the Moon will only be 10° high at that time,
so there's a good chance the cloud-catching
peaks of the Olympic Mountains will interfere.
Better chances are in Alaska. The Moon will
be more than 20° high for Juneau at disappearance and still 15° high at reappearance:
not ideal conditions, but not impossible.
For those watching close to moonset and
sunrise, optical aid is required. Alaska sees both
events in darkness, but a telescope or at least
good binoculars will be needed to spot the star
as it nestles up to the Moon's bright limb(s).
Some times: Seattle, disappearance 6:09
a.m., reappearance 6:56 a.m. PST; Vancouver,
BC, d. 6:05 a.m., r. 6:46 a.m. PST; Juneau,
d. 4:48 a.m., r. 5:39 a.m. AKST; Fairbanks, d.
4:33 a.m., r. 5:29 a.m. AKST; Anchorage, d.
4:38 a.m., r. 5:32 a.m. AKST.
Don't despair if you miss this one because
of your location. The Moon-Aldebaran occultation series is winding down, but we have a few
more to go before we see the last of them.
Saturday night December 30th offers a
good nighttime occultation for much of eastern
North America and a twilight-to-daylight
occultation for western North America. The
waxing gibbous Moon will be 90% lit when its
leading edge slips over Aldebaran. Even though
the star disappears at the dark edge, you'll
need binos to combat the bright Moon. The
reappearance on the bright limb, an hour or so
later, will be more difﬁcult to observe.
Some times: Halifax, disappearance 7:41
p.m., reappearance 8:33 p.m. AST; Boston, d.
6:29 p.m., r. 7:22 p.m. EST; Montreal, d. 6:28
p.m., r. 7:27 p.m. EST; Washington, DC, d.
6:19 p.m., r. 7:09 p.m. EST; Toronto, d. 6:28
p.m., r. 7:27 p.m. EST; Atlanta, d. 6:09 p.m.,
r. 6:52 p.m. EST; Chicago, d. 5:13 p.m., r. 6:10
p.m. CST; Kansas City, d. 5:09 p.m., r. 6:20
p.m. CST; Denver, d. 4:06 p.m., r. 5:00 p.m.
MST; Tucson, d. 3:58 p.m., r. 4:51 p.m. MST;
Edmonton, d. 4:29 p.m., r. 5:18 p.m. MST.
s k y a n d t e l e s c o p e . c o m * D E C E M B E R 2 0 17

49
http://www.skyandtelescope.com/algol http://www.skyandtelescope.com
Sky and Telescope - December 2017

Table of Contents for the Digital Edition of Sky and Telescope - December 2017
