Sky and Telescope - September 2015 - 47

Fred Schaaf

To ﬁnd out what's visible in the sky from your location, go to skypub.com/almanac.

O R B IT S O F THE P L ANE T S
The curved arrows show each planet's movement
during September. The outer planets don't change
position enough in a month to notice at this scale.

December
solstice

Mars

Venus

September, while its phase thickens from
approximately 9% to 34% lit. Viewers
around latitude 40° north see Venus rise
less than 2 hours before the Sun at the
beginning of the month but about 3½
hours before at month's end. It's almost
30° high an hour before sunrise on the
last morning of the month.
Mars is as high as, or higher than,
Venus through the ﬁrst week of September. On August 29th, Venus passed 9½°
south of Mars during a south-curving retrograde (westward) motion that continues
through September 5th. For the rest of
this month, Mars keeps its lead on Venus
as they move eastward with direct motion
against the background of stars. That
motion carries magnitude +1.8 Mars to
within 1° of magnitude +1.3 Regulus on
the American mornings of the 24th and
25th, when the pair is equidistant from
Venus and Jupiter. Their close approach
accentuates the orange-gold of Mars and
blue-white of Regulus.
Jupiter, at magnitude -1.7, is the last

Moon
Sept 20

March
equinox

Mercury

Jupiter

Uranus

Saturn

Neptune
Pluto

planet to rise in the morning, coming
up less than half an hour before the
Sun on September 1st but more than 2
hours before the Sun on September 30th.
Around the latter date, Jupiter forms a
beautiful curved line with Mars, Regulus,
and Venus above it.

Dawn, Sept 25

1 hour after sunset

1 hour before sunrise
Venus

LEO
Moon
Sept 18

Mars
Antares

Regulus

Saturn

Less than
1° apart!

SCORPIUS

Looking Southwest

Earth

June solstice

Dusk, Sept 18 -20

Moon
Sept 19

Sept.
equinox

Sun

Jupiter

Looking East

SUN AND MOON
The Sun arrives at the equinox at 4:21
a.m. EDT on September 23rd, marking
the beginning of autumn in the Northern
Hemisphere and spring in the Southern Hemisphere. The Sun is partially
eclipsed from parts of southern Africa
and Antarctica on the 13th.
The Moon is totally eclipsed on the
American evening of Sunday, September
27th, which is the European morning of
Monday the 28th; see page 26. This full
Moon is a Harvest Moon as well as the
biggest of the year, with the year's closest perigee occurring less than an hour
before the moment of full Moon.
The Moon is a slender waning crescent between Venus and Mars as the two
planets rise in the east before dawn on
the 10th. The next day, the Moon is to the
right of Regulus and appears even thinner. Late in the dawn, and very low in the
sky on the 12th, a subtle sliver Moon, less
than a day from new, may be detectable
to the lower right of Jupiter. The waxing
crescent is close to and upper right of
Saturn at dusk on the 18th. ✦

Sk yandTelescope.com September 2015

47
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Sky and Telescope - September 2015

Table of Contents for the Digital Edition of Sky and Telescope - September 2015
