Sky & Telescope - December 2018 - 46

DECEMBER 2018 OBSERVING
Sun, Moon & Planets by Fred Schaaf
To find out what's
visible in the sky
from your location,
go to skypub.com/
almanac.

Conjunction Couplet
As we head into the darkest time of the year, the planets keep us busy with their nightly capers.

n the ﬁnal month of 2018, the planets
offer an interesting assortment of
sights at both dusk and dawn - including two very close planetary conjunctions. At dusk, Saturn is very low in
the southwest until it drops completely
from view around mid-month. Mars
remains well-positioned, standing at
its highest in the south at nightfall and
passing extremely close to dim Neptune early in the month. In the dawn
sky, Venus is spectacularly bright and
impressively high. Very far to the lower
left of Venus, Mercury climbs to a good
apparition in the southeast, followed
by brighter Jupiter, which closely passes
Mercury a few days before Christmas.

DUSK ONLY
Saturn starts December setting about
two hours after the Sun. By the end of
the ﬁrst week of the month the mag-

α Cap

nitude-0.5 planet stands only about
8° or 9° high in the southwest just
30 minutes after sunset (use binoculars). By around mid-month the ringed
planet has fallen too deep into the
Sun's afterglow to ﬁnd. This year, 2018,
is one of only two between 1961 and
2040 in which Saturn doesn't reach
conjunction with the Sun - but it will
on January 2, 2019.

DUSK TO MIDNIGHT
Mars races east from Aquarius into
Pisces in December and sets at almost
the same time - around 11:30 p.m. -
every night during the month. The time
that Mars reaches the meridian in the
south does change a little, though, from
about 6 p.m. to 5:15 p.m. - but remains
excellent, around nightfall, throughout
December. Unfortunately, even having
Mars at its highest doesn't guarantee

seeing much on its surface in amateur
telescopes, because the planet dwindles
from about 9″ to 7½″ in diameter this
month. Mars, like a fading ember, also
decreases in brightness, from magnitude -0.1 to +0.5.
One special telescopic sight to
look for this month is an ultra-close
conjunction of Mars and Neptune.
The two are closest together - just 2′
apart - around 15 UT (10 a.m. EST) on
December 7th. In the Americas on the
evening of December 6th, the separation between the planets is a little more
than 20′ shortly after sunset, and on
the evening of the 7th they are even
closer, a mere 15′ apart.
Uranus, on the border of Pisces
and Aries, is highest a few hours after
evening twilight ends. Finder charts for
it and Neptune are in the September
issue, pages 48-49.

Dusk, Dec 8 -10

Dusk, Dec 13 -15

Dawn, Dec 15

30 minutes after sunset

1 hour after sunset

45 minutes before sunrise
Venus

β Cap
β Lib

Moon
Dec 10

Mars

10°
Moon
Dec 15

Moon
Dec 9

Saturn

α Lib

Moon
Dec 14
Moon
Dec 8

Moon
Dec 13

Mercury
Jupiter

Looking Southwest

DECE MBE R 2 018 * SK Y & TELESCOPE

Looking South, halfway up

Looking Southeast

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Sky & Telescope - December 2018

Table of Contents for the Digital Edition of Sky & Telescope - December 2018