Sky and Telescope - August 2016 - 46

OBSERVING

Sun, Moon & Planets

August's Double Convergences
Observe a series of planetary get-togethers this month.
Welcome to a short but wonderful burst
of planetary conjunctions. Some occur
very low in evening twilight - including
an ultra-close meeting of planets Venus
and Jupiter. But in addition to the groupings of Venus, Jupiter, and Mercury (and
Denebola

Dusk, Aug 4-5
20 minutes after sunset

Jupiter
Moon
Aug 5
Mercury
Moon
Aug 4

Venus
Regulus

Looking West

DUSK
On August 1st, Jupiter, Mercury,
Regulus, and Venus - in that order,
from upper left to lower right - form
a line nearly 27° long in the west after
sunset. But look early in twilight and
bring binoculars, because Venus is only
about 4° high even just 20 minutes after
the Sun goes down, as seen from latitude 40° north. Magnitude -0.1 Mercury
gleams about 8° upper left of magnitude
-3.9 Venus, which sets a bit more than
45 minutes after the Sun. Mercury sets
approximately 15 minutes later, and Jupiter follows in another 45 minutes.

Dusk, Aug 23

Dusk, Aug 11-13

30 minutes after sunset

1 hour after sunset
Moon
Aug 12

Moon
Aug 13

Regulus) very low in the west at dusk,
we'll also see Mars make a weeks-long
march in the south, moving from the
head of Scorpius to pass right between
Saturn and the Scorpion's heart, Marscolored Antares.

Moon
Aug 11
Saturn

Saturn
Mars

Mars
Antares

Antares

SCORPIUS
Cat's
Eyes

SCORPIUS

Looking South

46

August 2016 sky & telescope

Looking South-Southwest

Unfortunately for viewers at midnorthern latitudes, Mercury doesn't
appear any higher in the next few weeks,
even as it reaches greatest elongation on
August 16th. Venus, passing little more
than 1° from Regulus on August 4th and
5th (use optical aid to view the pairing),
edges just a bit higher as the weeks pass.
Jupiter, however, moves noticeably lower
in twilight each week, on its way to a
grouping of Venus, Mercury, and Jupiter
later in the month.
The spectacle of three planets passing
each other in the second half of the month
will present an observing challenge for
viewers at mid-northern latitudes.
On August 19th Mercury, at a maximum altitude of 6° and dimmed to
magnitude +0.3, shines its closest to
Jupiter, which is about 4° above it. Venus
is 8° right of Mercury, closer to the Sun.
On August 28th Mercury, seriously faded
to magnitude +0.8, comes its closest to
Venus, hovering about 5° below and left
of the brighter planet.
But the best conjunction for midnorthern viewers occurs on August 27th,
when Venus and Jupiter draw as close as
0.1°, depending on your viewing location.
From southern South America you can
see this meeting in a dark sky, where the
planets' lights will blend together when
viewed with the naked eye. Use binoculars to pick up the duo as the Sun sets
(but do not look at the Sun!). Telescopes
will show the disks of the two planets
together even in a fairly high-magniﬁcation ﬁeld of view. Jupiter's dim disk
measures about 31″ wide, the 92%-lit disk
of Venus 11″ wide.
On this same big evening, the trio of
Venus, Jupiter, and Mercury ﬁt within
their smallest circle of sky, just over 5° in
diameter. Venus and Jupiter remain 2°
apart or less from August 25th to 29th.
Sky and Telescope - August 2016

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