Sky & Telescope - August 2022 - 48

SATURN: CHRISTOPHER GO; TOOL: S&T
AUGUST 2022 OBSERVING
Celestial Calendar by Bob King
Saturn at Opposition
August presents a fine opportunity to view the planet, its
rings, and a handful of its brightest moons.
S
pectacular Saturn comes to opposition
on August 14th to the stridulations
of summer crickets and katydids.
Shining at magnitude +0.3 and presenting
rings spanning 42″, the planet sits
in eastern Capricornus. With the Sun
setting earlier each evening and generally
favorable late-summer weather,
there's no better time for some public
astronomy. If you own a telescope, I
encourage you to share Saturn with
everyone you can. More than a few
lifelong skywatchers got their first spark
of interest from a telescopic view of the
ringed wonder.
After narrowing to 12.3° in June,
the ring tilt increases to 13.9° in midAugust
with the north face exposed.
At low magnifications, telescopes show
only a single ring, but 100× or more will
subdivide it into three. (See the illustration
presented on page 29.) Cassini's
Division, a dark gap 0.8″ wide (at opposition),
separates the outer A ring from
the wider, brighter B ring. The innermost
C ring (also known as the crepe
ring) appears translucent. It's most
easily seen where it crosses in front of
Saturn's globe and looks deceptively like
a shadow or cloud belt. The C ring also
appears as a filmy, gray wedge in the
space between the inner edge of the B
ring and the planet's limb.
If you have a 10-inch or larger telescope
and rock-solid seeing conditions,
crank up the magnification to at least
Sky & Telescope's interactive online tool
allows observers to identify which of the five
brightest Saturnian moons is which. Alternatively,
the tool can be used as a planning aid to
show the arrangement of moons for a specific
time and date in the future.
48 AUGUST 2022 * SKY & TELESCOPE
midway in the A ring. Photographs often
show the feature well, but it's a serious
challenge for observers. Large scopes
used under ideal seeing conditions also
sometimes reveal tantalizing hints of
dark spokes streaking radially across the
broad B ring. See the feature on page 28
for more on this aspect of the rings.
Saturn's rings comprise billions of
pieces of mostly water ice that range in
size from sand grains to boulders as big
as houses. A ring form may symbolize
eternity, but astronomers have identified
a steady flow of ring rain - water
ice precipitating from the rings into the
planet's atmosphere - that will drain
away Saturn's signature feature within
the next 300 million years or less. So
much for eternity!
On nights of steady seeing, a 4-inch
Saturn shows off its rings, Equatorial Zone,
North Equatorial Belt, and North Polar Region
in this photo taken on April 18, 2022. The dark
band below the ring plane is the shadow of the
rings on the planet's cloudtops. The lighter gray
" shadow " just above the ring plane is the C
ring, also known as the crepe ring.
400× and try for the much narrower
Encke Gap, located within the outer
edge of the A ring. The tiny moon Pan,
just 35 kilometers (22 miles) across,
orbits within the gap and clears it of
material. You might also glimpse the
broader but low-contrast Encke Minima,
an ever-so-slightly darker band located
telescope used at magnifications of
100× or greater should reveal the
brownish North Equatorial Belt and
the gray " beanie cap " of the North
Polar Region. The South Equatorial
Belt remains hidden this apparition,
but patient observers may spy the pale,
gray band of the South Temperate Zone,
south of the ring plane.
Saturn is attended by (at last count)
83 moons, most of which are tiny.
However, eight of them are visible in
amateur telescopes, including Titan
(magnitude 8.4), Rhea (9.8), Tethys
(10.3), Dione (10.5), Iapetus (10.2 to
11.9), Enceladus (11.8), Mimas (13.0),
Sky & Telescope - August 2022

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