2019-08-01_Sky_and_Telescope

skyandtelescope.com • AUGUST 2019 47

brightness and size in August. The
golden world’s magnitude diminishes
from +0.2 to +0.3 and its equato-
rial diameter from 18.3′′ to 17.6′′ this
month. The rings remain tilted to 24.7°,
just a few degrees from their maxi-
mum angle. As with Jupiter this year,
Saturn’s southerly position calls for
observing it in the telescope when it’s
at its highest, crossing the meridian.
It transits around 11:30 p.m. daylight-
saving time at the start of August and
before 9:30 p.m. at month’s end. Saturn
shines between the little, dim Teaspoon
of Sagittarius and the bright handle of
the Teapot of Sagittarius. It continues to
retrograde and closes the gap from 5°
to 4° between itself and magnitude-2.1
Nunki, or Sigma (σ) Sagittarii. Saturn
sinks below the horizon around 4 a.m.
in early August and around 2 a.m. at
the end of the month.

NIGHT TO DAWN
Neptune reaches opposition on
September 10th but in August tran-
sits the meridian well after midnight
daylight-saving time. Uranus, two
magnitudes brighter than its fellow
ice giant Neptune, doesn’t rise until
after evening twilight begins and for

much of the month is at its highest

after the start of morning twilight. See

https://is.gd/urnep for a fi nder chart

to help you locate Neptune in Aquarius

and Uranus in Aries.

DAWN

Mercury has its best morning appari-

tions for observers at mid-northern

latitudes within a month or two of the

autumn equinox. On August 3rd it rises

more than an hour before the Sun but

has brightened only to magnitude 1.4 so

is just marginally visible (use binocu-

lars). On August 9th, however, Mercury

reaches a greatest western elongation

of 19° from the Sun, shines at zero

magnitude, and rises about 90 min-

utes before the Sun for viewers around

latitude 40°N. The little world is only

about 38% illuminated that morning.

It stands more than 10° above the east-

northeast horizon by 30 minutes before

sunrise that day. Mercury continues to

brighten throughout August but drops

deep enough into the Sun’s glow to be

lost from view by about August 26th

on its way to superior conjunction on

September 3rd.

MOON PASSAGES

The Moon is waxing gibbous, close

to Beta (β) Scorpii at nightfall on

August 8th. The next evening, the Moon

beams some 2° upper left of Jupiter

at nightfall, with Antares not too far,

around 6°, lower right of the planet. On

the 11th, the still-swelling Moon is not

far to the right of Saturn. The Moon is

a waning crescent around 2° above or

upper left of Aldebaran on the morning

of the 24th, and less than ½ ° from Zeta

(ζ) Tau on the morning of the 25th. Find

an even thinner lunar crescent lower

right of Pollux at dawn on the 28th.

¢FRED SCHAAF is the author of The

Starry Room: Naked Eye Astronomy in

the Intimate Universe, a collection of es-

says published by Dover Publications.

Jupiter

Saturn

Uranus

Neptune

Venus Mercury

Earth

Mars

March

equinox

June

solstice

December

solstice

Sept.

equinox

Sun

ORBITS OF THE PLANETS

The curved arrows show each planet’s movement during August. The outer planets don’t

change position enough in a month to notice at this scale.

skyandtelescope.com • AUGUST 2019 47

Dawn, Aug 10

30 minutes before sunrise

Castor

Procyon

Pollux

GEMINI

Mercury

Looking East-Northeast

Dawn, Aug 23 – 25

1 hour before sunrise

Aldebaran

Rigel

Betelgeuse ORION

TAURUS

Moon

Aug 23

Moon

Aug 24

Moon

Aug 25

Pleiades

Looking Southeast, high in the sky