Sky and Telescope - August 2017 - 46

AUGUST 2017 OBSERVING
Sun, Moon & Planets by Fred Schaaf

Eclipse, At Last
The "Great American" total solar eclipse is this month's star attraction.

re you ready to be awed? On Monday August 21st, the Moon paints
a streak of deep midday darkness from
Oregon to South Carolina with a swift
and narrow brush of umbra during the
long-awaited "Great American" total
eclipse of the Sun. All of the Americas
north of the equator get a partial eclipse.
This month also features a partial lunar
eclipse for the opposite side of the world,
visible across most of the Eastern Hemisphere on the night of August 7-8.
But what are the planets up to in
this month of Sun and shadow? Jupiter
appears in the west-southwest at nightfall and sets in late evening. Saturn
shines in the south at dusk and sets
in the middle of the night. Venus rises
an hour or so before morning twilight

Dusk, Aug 1- 4
1 hour after sunset

Moon
Aug 3

Moon
Aug 4

begins, beaming high in the east as sunrise nears. Mars and Mercury are too
near the Sun for viewing this month,
outside of the brief minutes at totality
during the solar eclipse.

AT TOTA LIT Y
Mars was in conjunction with the Sun
on July 27th and is lost from view in the
solar glare throughout August - except
when its 1.8-magnitude light might
be glimpsed about 8° right of the Sun
during the total eclipse on August 21st.
Brilliant Venus, a bit more than four
times farther right from the Sun than
Mars, will be easy to see during totality. Depending on the transparency of
your sky, you may be able to catch Venus
when the Sun is only 85-90% covered by
Moon
Aug 2

Moon
Aug 1

Saturn
Antares

SCORPIUS

10°

S A G I T TA R I U S

Looking South-Southeast

C a t 's
Eyes

Looking South

p These 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 fist at arm's length. For clarity, the Moon is shown three times its actual apparent size.

A U G U S T 2 0 1 7 * SK Y & TELESCOPE

the Moon. Mercury, at 4th magnitude,
shines too faintly, and Jupiter, about
77° from the Sun, is bright but low in
the southeast. Most tantalizing is Regulus, magnitude 1.4, only about 1° left of
the eclipsed Sun's disk. That's about two
solar diameters. Binoculars will help.

EVENING
Jupiter declines from about 22° to 11°
high in the southwest when observed 45
minutes after sunset in August. Jupiter
fades from magnitude -1.9 to -1.7 and its
disk shrinks from about 34″ to 32″ wide
over the course of the month. The gap
between Jupiter and Spica narrows from
about 8° to 4°. On August 10th binoculars show Jupiter at its closest (0.6°) to
4th-magnitude Theta (θ) Virginis.
Saturn, magnitude +0.4, hovers in
southeastern Ophiuchus this month,
glowing at its highest (about 27°) due
south in late twilight.
Saturn's rings will appear slightly
more open in October, when they reach
maximum tilt (27.0°) from our perspective for the ﬁrst time since 2002. But
we can catch Saturn higher at nightfall
now, when the ring tilt is essentially
the same. The planet's globe shrinks
only slightly in the eyepiece this month,
from 18″ to 17″ in equatorial diameter.
Saturn becomes stationary in right
ascension and ecliptic longitude on
August 25th. The next day, the magnitude +0.4 world stands a minimum
12.6° upper left of distinctly less bright
Antares; it then starts moving away from
the star with direct (eastward) motion.

NIGHT
Neptune, in Aquarius, rises during
evening twilight and ﬁnishes the month

Sky and Telescope - August 2017

Table of Contents for the Digital Edition of Sky and Telescope - August 2017