2019-08-01_Sky_and_Telescope

46 AUGUST 2019 • SKY & TELESCOPE

AUGUST 2019 OBSERVING
Sun, Moon & Planets by Fred Schaaf

quThese 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 fi st at arm’s length. For clarity, the Moon is shown three times its actual apparent size.

T

his is the summer of the terrestrial

planets Venus and Mars huddling

out of sight near the Sun while the

gas giant planets Jupiter and Saturn

promenade in glorious view for much

of the night.

The last of the fi ve classic bright plan-

ets, Mercury, spends the summer dodg-

ing in and out of the solar glare. And

though it’s most often in that glare and

not easily visible, August is an exception:

Mercury spends much of the month giv-

ing us a fi ne apparition before sunrise.

DAYTIME

Venus and Mars are both lost in the

glare of the Sun throughout August. On

August 26th, Mars reaches aphelion, its

Two Large, One Small

The two gas giants continue to enthrall us during the earlier part of the night,

while plucky Mercury delights us in the morning.

farthest from the Sun in space, when

it’s at a distance of 1.67 a.u. from our

star. Then, amazingly, just 7 days later,

Mars comes to conjunction with the

Sun and is at almost its very farthest

possible from Earth, 2.67 a.u.

Mars doesn’t emerge into visibility

until the middle of October when it

does so at dawn, but Venus starts com-

ing into view at dusk in mid-September.

DUSK TO NIGHT

Jupiter lingers near Antares all month.

It retrogrades to a minimum of 6¾°

from the star on August 11th before

beginning to ever so slowly move east-

ward and away from Antares. The giant

planet fades a bit — from magnitude

–2.4 to –2.2 — and shrinks from about

43 ′′ to 39′′. But the key observational

fact about Jupiter this month is that

it’s highest around nightfall — which

is therefore the prime time to look for

detailed views of the planet’s cloud

features in the telescope. As soon as

evening twilight ends, astrophotogra-

phers at dark sites can go for majestic

views of Jupiter’s brilliant beacon sur-

rounded by the bright and dark Milky

Way clouds of southern Ophiuchus (see

S&T: July 2019, p. 57). The setting time

of Jupiter backs up from about 2 a.m. to

midnight daylight-saving time during

the course of August.

Saturn was at opposition on July 9th

but only loses a little bit of apparent

46 AUGUST 2019 • SKY & TELESCOPE

To fi nd out what’s

visible in the sky

from your location,

go to skypub.com/

almanac.

Aug 2

Antares

SAGITTARIUS

Jupiter

Saturn

Looking South-Southeast Looking South

Around 9 pm

SCORPIUS

Cat’s

Eyes

10 °

Antares

Jupiter

Moon

Moon Aug 8

Aug 9

Looking South

Aug 8–9

Around 9 pm

SCORPIUS

Cat’s

Eyes