Sky and Telescope - October 2016 - 46

OBSERVING

Sun, Moon & Planets

Tower of Light
Saturn, Venus, and Antares fall into line near the end of October.
At dusk this October, Venus shines
brilliantly low in the southwest. It needs
almost the entire month to close the gap
between itself and Saturn before passing
dramatically between the fairly closely
paired Saturn and Antares.
Meanwhile Mars, still a bit brighter
than Saturn, continues to move eastward,
away from the Saturn-Antares duo, to
glow like a ﬁrespark in the south-southwest at nightfall.
At dawn in the ﬁrst week of October,
lustrous Mercury remains alone low in
the east. But Jupiter soon comes into view
and passes very close to Mercury's right
on October 11th. As the month progresses,
Mercury disappears into the sunrise while
Jupiter rises earlier and reaches higher.

DUSK
Venus, low in the southwest after sunset,
creeps a little higher as October progresses, improving by month's end to
about 10° high 45 minutes after sunset for

observers around latitude 40° north. Telescopes reveal the gibbous disk of Venus
changing only gradually, growing from
12″ to 14″ wide while its phase decreases
from about 86% to 78% lit.
A few days into the month and well
into Libra, Venus passes below the wide
double star Alpha (α) Librae (Zubenelgenubi). They're less than 1° apart on the
5th. Around October 20th Venus crashes
through the "fence" of stars that forms
Scorpius's head, brushing very close to
the bright and unpredictable variable star
Delta (δ) Scorpii (Dschubba).
Venus is 3° upper right of Antares on
the American evenings of October 25th
and 26th. The most exciting event, however, happens on the 27th, when Venus
passes midway through the gap between
Saturn and Antares, forming a nearly
vertical line with them low in twilight.
In this tower of bright objects, Saturn
shines at magnitude +0.5, Venus at -4.0,
and Antares at +1.0. Thus Venus burns

Dusk, Oct 3 - 6

Moon
Oct 6

45 minutes after sunset
Moon
Oct 5

Saturn

SCORPIUS

100 times brighter than Antares. Poor
Antares is also the lowest of the three by
that day - it's already less than 10° high
only 30 minutes after sunset.
Saturn was closest to Antares back on
September 11th, when it was 6° northnortheast of the star. The ringed planet
is moving, slowly but surely, eastward
and away from Antares, but at the end of
October they're still close, only 7° apart.
Saturn's globe is less than 16″ wide
this month and subtly shrinking, but its
rings remain open and beautiful at 26°
from edge on. At the start of October,
however, Saturn stands only about 20°
high in the southwest an hour after sunset. By month's end it's only half that.

EVENING
Mars fades from magnitude +0.1 to +0.4
in October. The ﬁre-colored planet races
across most of Sagittarius during the
month. It starts October lower left of
M8, the Lagoon Nebula. Mars is farthest
Moon
Oct 9

Dusk, Oct 7-9
Moon
Oct 8

1 hour after sunset
Moon
Oct 7

Moon
Oct 4

β Lib

10°

Mars

Antares

h

Moon
Oct 3

α Lib

S A G I T TA R I U S
Venus

Looking Southwest

Looking West-Southwest

These scenes are drawn for near the middle of North America (latitude 40° north, longitude 90°
west); European observers should move each Moon symbol a quarter of the way toward the one
for the previous date. In the Far East, move the Moon halfway. The blue 10° scale bar is about the
width of your ﬁst at arm's length. For clarity, the Moon is shown three times its apparent size.

46

October 2016 sky & telescope

Looking South-Southwest
Sky and Telescope - October 2016

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