Sky and Telescope - August 2018 - 47

falling just short of reaching M8 (the
Lagoon Nebula) and M20 (the Triﬁd
Nebula). The ringed world is at its notvery-high highest around 10:30 p.m. as
August starts and around 8:30 p.m. as
the month ends. Saturn's brightness
fades from magnitude +0.2 to +0.4,
and its equatorial diameter decreases
slightly from 18″ to 17″ - but its rings
remain magniﬁcently prominent, tilted
at more than 26°.
Mars was at opposition on July 27th 
and its closest to Earth in 15 years on
July 31st. The Red Planet remains
brighter and bigger than it has been
since 2003 for the entire month of
August. Rising just after sunset as
August begins, Mars crosses the meridian in the south after 12:30 a.m. in
early August but before 10:30 p.m. as
the month ends.
Mars starts August still burning at
its peak magnitude of -2.8 and by the
ﬁnal days of the month glows at -2.2,
still brighter than Jupiter. Telescopes
reveal its globe to be more than 24″
wide on August 1st and 21″ wide on
August 31st. For speciﬁc details on
making telescopic observations of Mars
and determining which side of the
planet is facing you at a given time, see
https://is.gd/marsproﬁler and the July
issue, page 22.

December
solstice

Uranus

March
equinox

Jupiter

Sun

Sept.
equinox

Earth

Neptune

Saturn

Mercury

Venus
June
solstice

Mars

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.

The biggest problem for viewers
around latitude 40° north or farther
north is the extreme southerly declination of Mars this month. In addition to
being near the southernmost part of the
zodiac, it's also 6° south of the ecliptic.
The tiger-colored planet moves from
southern Capricornus back into Sagittarius, but halts its retrograde motion
on August 28th and then resumes direct
motion (eastward against the background stars).
Neptune and Uranus rise in the
evening this month and are highest a
few hours before dawn (Neptune) or

before sunrise (Uranus). Finder charts
for these two distant worlds appear at
https://is.gd/urnep.

DAWN
Mercury leaps up from inferior conjunction on August 9th and becomes
visible after the 20th; binoculars will
help. By the 26th, the date Mercury
reaches greatest western elongation
18° from the Sun, the planet is brighter
than zero magnitude and rises just
before 5 a.m., right after the start of
astronomical twilight.

SUN AND MOON
Dusk, Aug 31
Castor

30 minutes after sunset

β Lib

Pollux

Dawn, Aug 26

Jupiter

45 minutes before sunrise

α Lib
Procyon

Spica
Mercury

Looking East

Venus

Looking Southwest

The Sun is partially eclipsed by the
Moon on August 11th across Greenland, northern Europe, most of Russia,
and northeast Asia.
The Moon is a waning crescent
entering the Hyades at dawn low in the
east on August 6th. The waxing crescent Moon is around 10° right of Venus
at dusk on August 13th and 7° above
Venus on August 14th. The waxing
gibbous Moon shines less than 4° right
of Saturn at nightfall on August 20th.
The fattening Moon is around 9° upper
right of Mars at nightfall on August
22nd and then 8° upper left of Mars
the next night. 
¢ FRED SCHAAF teaches astronomy at
Rowan University and Rowan College
in Gloucester County, both in southern
New Jersey.
sk yandtelescope.com * AUGUST 2 018

47
https://www.is.gd/urnep https://www.is.gd/marsprofiler http://www.skyandtelescope.com
Sky and Telescope - August 2018

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