Sky & Telescope - October 2023 - 46

OCTOBER 2023 OBSERVING
Sun, Moon & Planets by Gary Seronik
To find out what's
visible in the sky from
your location, go to
skyandtelescope.org.
The Moon Meets Jupiter . . . Twice
Good timing results in a mirrored pair of eye-catching conjunctions.
SUNDAY, OCTOBER 1
It's handy when a month begins with an
eye-catching close conjunction involving
the Moon and a bright planet. On
this evening, that planet happens to be
Jupiter, which gleams at magnitude
-2.8. Why is that handy? Because the
Moon returns to roughly the same place
in the sky in a span of time known as a
sidereal month, which is 27.3 days long.
The important thing to note here is
that a sidereal month is shorter than a
calendar month. As a result, we get not
one but two Moon-Jupiter pairings in
October. (See the facing page for details
on the second one.)
This evening, look toward the eastnortheast
to catch a waning gibbous
Moon (two days past full) and Jupiter
rising just 2° apart - the Moon will
pop up about 10 minutes before the
planet. The gap between the twosome
will more than double as they arc across
the sky together tonight, thanks to the
Moon's eastward motion along the
ecliptic. That's why the earlier you look,
the more spectacular the sight will be.
MONDAY, OCTOBER 2
A little more than 24 hours after its
encounter with Jupiter, the Moon pairs
up with the Pleiades. This conjunction
won't be as interesting as the previous
night's, however. The lunar disk
remains very bright, and the cluster's
stars have a tough time competing
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.
Oct 1 - 2
10:30 p.m.
Moon
Oct 1
Jupiter
Pleiades
Moon
Oct 2
CETUS
10°
TAURUS
Aldebaran
Castor
Pollux
GEMINI
Denebola
Moon
Oct 7
Moon
Oct 12
Moon
Oct 6
Moon
Oct 11
Oct 6 - 7
1 a.m.
LEO
against the Moon's glare. That's why
you'll want to grab your binoculars
before heading outdoors - the extra
light grasp and magnification that binos
offer go a long way toward making the
event viewable. Thankfully, the objects
are close together: Just 2° separates the
Moon from 2.9-magnitude Alcyone, the
brightest Pleiad. That's close enough
that the entire cluster and the Moon
comfortably fit together in the field of
view of 10×50s.
As the night of the 2nd transitions
into the morning of the 3rd, the lunar
disk shifts from lying under the Pleiades
to sitting left of the cluster, but all the
while remaining close enough to fit
within a single binocular field of view.
Dawn, Oct 10 - 12
1 hour before sunrise
Regulus
Moon
Oct 10
Venus
Looking East
Looking East-Northeast
46
OCTOBER 2023 * SKY & TELESCOPE
Looking East

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Sky & Telescope - October 2023

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