Sky and Telescope - October 2016 - 47

Fred Schaaf

To ﬁnd out what's visible in the sky from your location, go to skypub.com/almanac.

December
solstice

O R B IT S O F THE P L ANE T S
The curved arrows show each planet's movement
during October. The outer planets don't change
position enough in a month to notice at this scale.

Earth
Mercury

March
equinox

south of the ecliptic on October 3rd.
On the 6th it passes just 0.2° south of
Lambda (λ) Sagittarii, the top star of the
Sagittarius Teapot. During the second
half of October, it passes over the Teapot's
bright handle and treks a few degrees
below the dimmer Teaspoon asterism.
But good telescopic viewing is just a
memory; Mars shrinks to less than 8″
wide over the course of the month. The
Red Planet reaches perihelion, its closest
to the Sun in space, on October 29th.
Magnitude-14.2 Pluto resides dimly in
the bowl of the Sagittarius Teaspoon; see
the ﬁnder chart in the July issue, page 48.

Sept.
equinox

Sun

Mars
Venus
June solstice

Uranus

Jupiter
Saturn

Neptune

Pluto

NIGHT
Uranus comes to opposition in Pisces on
October 15th, so it's technically visible all
night long this month. At magnitude +5.7,
with a 3.7″-wide disk, however, the ice
giant is best seen when high - in other
words, in the middle of the night.
Neptune, in Aquarius and several
hours ahead of Uranus, shines two

Dawn, Oct 11
30 minutes before sunrise

Denebola

Regulus

magnitudes fainter and appears less than
2/3 as wide, but transits during more convenient hours. Finder charts for Uranus
and Neptune are on page 50.

DAWN
Mercury and Jupiter trade roles in the
October dawn. The month starts with
only Mercury visible, just past the peak of
its ﬁnest morning apparition of the year
for observers at mid-northern latitudes. It
shines about 8° above the due-east horizon 45 minutes before the ﬁrst sunrise of
the month. By about October 8th Jupiter
emerges below it, moving higher each
day as Mercury gets lower. On the Ameri-

MOON PA SSAGES

Dusk, Oct 27
30 minutes after sunset

Saturn
Less than
1° apart!
Mercury

Venus
Antares

Jupiter

Looking East

can morning of October 11th, magnitude
-1.1 Mercury beams just 0.8° left of
magnitude -1.7 Jupiter. Bring binoculars
or a telescope and hope for very clear air;
they'll be only about 5° above the horizon in the bright sky 30 minutes before
sunrise. Telescopes may reveal Mercury's
90% illuminated disk to be only 5″ wide
compared to Jupiter's 31″.
Mercury appears lower each morning
thereafter, becoming lost in the sunrise
by mid-month before dropping through
superior conjunction with the Sun on
October 27th. In contrast, Jupiter continues to climb, rising almost 2½ hours
before the Sun at month's end.

Looking Southwest

The crescent Moon waxes above and
right of Venus on the evening of October
3rd, right of Saturn on October 5th, and
upper left of Saturn on October 6th. The
ﬁrst-quarter Moon lies rather far upper
right of Mars on October 7th, then similarly far upper left of it the next night. A
widely visible occultation of Aldebaran by
the waning gibbous moon occurs on the
night of October 18-19; see p. 48. At dawn
on October 28th, a hair-thin waning
crescent hangs very close to the lower left
of Jupiter. ✦
Sk yandTelescope.com October 2016

47
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Sky and Telescope - October 2016

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