Sky & Telescope - USA (2019-09)

46 SEPTEMBER 2019 • SKY & TELESCOPE

SEPTEMBER 2019 OBSERVING
Sun, Moon & Planets by Fred Schaaf

M

uch of the night is starved of

bright planets this month. Mer-

cury and Mars continue to be hidden

from view in the solar glare. Venus does

gleam back into sight in late September

but early in dusk, very low in the Sun’s

afterglow. Jupiter burns in the southwest

as evening twilight fades, while Saturn

shines in the south — but even Saturn is

setting around midnight at month’s end.

DUSK

Venus went through superior conjunc-

tion on August 14th but in the second

half of September comes back into view

after sunset for observers at mid-north-

ern latitudes. After two months of being

out of sight at these latitudes, Venus is

still diffi cult to catch due to the shal-

low angle of the zodiac with respect to

the sunset horizon at this time of year.

Venus sets only about 30 minutes after

the Sun at month’s end. On a clear day

in the latter part of September, however,

the brilliance of this –3.9-magnitude

planet stands out briefl y down near the

western horizon, even in bright twilight.

Mercury is at superior conjunction

with the Sun on the night of Septem-

ber 3–4. Only with optical aid at more

southerly latitudes will observers be able

to catch fainter Spica a little more than

1° southwest of Mercury on the Ameri-

can evening of September 28th.

DUSK THROUGH EVENING

Jupiter and Saturn have been the

great planetary attractions of summer

nights. Now, as summer ends, they’re

setting earlier. Jupiter begins Septem-

ber just past the meridian in the south

as it comes into view early in evening

The Month of the Harvest Moon

The smaller planets are largely missing from September’s skies, but the two gas giants

are joined by the two ice giants — and the full Moon heralds the harvest.

twilight. Its magnitude dims from –2.2

to –2.0 this month, but of course that’s

plenty bright enough for it to stand out

brilliantly in southwestern Ophiuchus

as it continues to move slowly away

from Antares. Jupiter’s angular diameter

decreases from 39′′ to 36′′ in September.

It reaches eastern quadrature (90° east

of the Sun) on September 8th, so this is

a good month to see eclipses of the Gali-

lean moons (see page 51). By the end of

the month the planet sets not long after

46 SEPTEMBER 2019 • SKY & TELESCOPE

To fi nd out what’s

visible in the sky

from your location,

go to skypub.com/

almanac.

Dusk, Sept 4–8

45 minutes after sunset

Antares

SAGITTARIUS

Cat’s Eyes SCORPIUS

Jupiter

Saturn MoonSept 4

Moon

Sept 5

Moon

Moon Sept 6

Sept 7

Moon

Sept 8

Looking South Looking South-Southwest

10 °

Sept 12 –16

Fomalhaut

PISCES

Moon

Sept 12

Moon

Sept 13

Moon

Sept 14

Moon

Moon Sept 15

Sept 16

Looking East Looking East-Southeast

Circlet

Around 9 pm

Notice the Harvest Moon effect:

A nearly full Moon appears low

in the sky at the same time on

many consecutive evenings.