Sky and Telescope - October 2017 - 46

OCTOBER 2017 OBSERVING
Sun, Moon & Planets by Fred Schaaf

A Pretty Pair
Venus and Mars dance at dawn. Saturn sets early in the evening.

ercury is too close to the Sun to
see properly this month, and the
other bright planets hang low at either
dusk or dawn. Saturn remains visible
in the southwest for a few hours after
sunset, then the sky is devoid of bright
planets until Venus and Mars rise
shortly before morning twilight.
But there's one exceptionally tight
conjunction of planets in October, as
well as several pairings of planets and
stars with the Moon.

DUSK AND EVENING
Jupiter remains detectable for just the
ﬁrst few days of October, very low in
the bright afterglow of sunset. The giant
planet goes though conjunction with
the Sun on October 26th, then around
November 7th returns to visibility low
in the east at dawn, at least for the
sharp-eyed among us.
Saturn glows low in the southwest
during twilight all October, dropping

lower every week. Saturn sets more than
3½ hours after the Sun on October
1st, but only 2½ on October 31st. The
ringed planet's brightness lingers at
magnitude +0.5 all autumn as it creeps
eastward in Ophiuchus toward Sagittarius. The red supergiant Antares shines
far - about 14° - to the lower right of
Saturn at nightfall in early October.
Saturn's rings are at their maximum
tilt of 27° this month. Too bad the
planet's altitude an hour after sunset
is only about 20° high for observers around latitude 40° north. From
much farther south, where the planet is
higher in early evening, telescope users
have a better chance of steady seeing on
some evenings.

NIGHT
Uranus reaches opposition on October
19th and is therefore visible all night -
though it's best observed when highest
in the south near 1 a.m. local daylight-

saving time. The blue-green world
shines at magnitude 5.7 and appears
3.7″ across in telescopes.
Neptune shines only a sixth as
brightly (magnitude 7.8) as Uranus
because of its greater distance from
both Earth and Sun. It was at opposition on September 5th, so it's now highest in mid- to late evening.
Uranus is in Pisces, about 2° from
Omicron (ο) Piscium; Neptune is less
than 1° southeast of Lambda (λ) Aquarii this month. See page 51 for ﬁnder
charts for both planets.
Asteroid 2 Pallas, one of the largest asteroids in the solar system, is at
opposition on October 29th, shining
at magnitude 8.3 in Eridanus. Pallas's
highly inclined orbit places it extremely
far south of the ecliptic at this opposition, around declination -20° near Tau3
(τ3) Eridani (also known as Angetenar).
A night of good transparency will help
you with this observation.

Dusk, Oct 6

Dawn, Oct 8-11

1 hour after sunset

10°

OP HIUCHUS

1 hour before sunrise

TA U R U S

Moon
Oct 11

Saturn
Betelgeuse

Moon
Oct 10

Pleiades
Aldebaran

Antares

SCORPIUS

ORION

Moon
Oct 9
Moon
Oct 8

Looking Southwest
46

O C T O B E R 2 0 17 * S K Y & T E L E S C O P E

Rigel

Looking Southwest, high in the sky

Sky and Telescope - October 2017

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