Sky and Telescope - May 2018 - 49

Central meridian (CM)

Belts (dark)
One of the neat things about Jupiter is that
SOUTH
South Polar Region
our view of it changes relatively quickly. A revolution takes just under 10 Earth hours, so if you
S. S. Temperate Belt
Zones (bright)
observe early, then return to the planet later that
S. Temperate Zone
S. Temperate Belt
night, you'll see a decidedly different picture. The
Great Red Spot
S. Tropical Zone
diagram at the right shows Jupiter's main markDirection of
S. Equatorial Belt
rotation
Equatorial Zone
ings. Through a small scope, you should be able
Equatorial Band
to see the two major cloud bands, the South and
N. Tropical Zone
N. Equatorial Belt
North Equatorial Belts. From there, it's a matter
N. Temperate Zone
N. Temperate Belt
of spotting subtleties. Jupiter's belts, both equatoN. N. Temperate Belt
rial and temperate, are slightly ruddy or beige in
the eyepiece. They're separated by brighter, whiter
North Polar Region
bands called zones. Distinguishing white-ish
NORTH
zones from wheat-ish belts is a full night's work.
Within the zones and belts rage storms. Look
p The features of Jupiter change in intensity, size, and position over
for these ovals, tight gatherings of clouds that dot Jupitime; this basic schema should help you identify what you see in your
ter's bands. White ovals, which often develop in the South
eyepiece. South is up to match the view in many telescopes. Features
rotate from celestial east to west.
Temperate Belt, can really "pop" in the eyepiece. Ovals can
also be red, as in the Great Red Spot, or gray. Barges resemble
compressed ovals; they're dark and red, but somewhat linear
22:47; 24, 8:42, 18:38; 25, 4:33, 14:29; 26, 0:25, 10:20, 20:16;
or blocky. Study the belts for variations in color caused by
27, 6:11, 16:07; 28, 2:03, 11:58, 21:54; 29, 7:50, 17:45; 30,
rifts, long, bright streaks that stretch along the darker bands.
3:41, 13:36, 23:32; 31, 9:28, 19:23.
Readily apparent in images but more elusive to the eye are
These times assume that the spot will be centered at System
festoons, tendril-like blue-gray features that angle into zones
II longitude 288°. If the Red Spot has moved elsewhere, it will
from a belt.
transit 1 2/3 minutes earlier for each degree less than 288° and
1 2/3 minutes later for each degree more than 288°.

G A N Y MEDE: DA MIA N PE ACH / CHILESCOPE TE A M;
JUPITER DIAG R A M: G REGG DINDER M A N / S&T

The Great Red Spot
If you time your observing to coincide with the transit of
the Great Red Spot (GRS), the changes on the planet's face
become even more obvious. The GRS, which sits in a pocket
between the South Equatorial Belt and the South Tropical
Zone called "Red Spot Hollow," can be a challenge for observers with small scopes. Your best chance at seeing it is within
an hour of the time it crosses the planet's central meridian.
Here are those crossing times, in Universal Time, as predicted
for April and May. The dates, also in UT, are in bold. (Eastern
Daylight Time is UT minus 4 hours.) For more on the GRS,
see page 52.
April 1, 0:11, 10:07, 20:02; 2, 5:58, 15:54; 3, 1:49, 11:45,
21:40; 4, 7:36, 17:32; 5, 3:27, 13:23, 23:18; 6, 9:14, 19:10; 7,
5:05, 15:01; 8, 0:56, 10:52, 20:47; 9, 6:43, 16:39; 10, 2:34,
12:30, 22:25; 11, 8:21, 18:17; 12, 4:12, 14:08; 13, 0:03, 9:59,
19:54; 14, 5:50, 15:46; 15, 1:41, 11:37, 21:32; 16, 7:28, 17:24;
17, 3:19, 13:15, 23:10; 18, 9:06, 19:01; 19, 4:57, 14:53; 20,
0:48, 10:44, 20:39; 21, 6:35, 16:31; 22, 2:26, 12:22, 22:17;
23, 8:13, 18:08; 24, 4:04, 14:00, 23:55; 25, 9:51, 19:46; 26,
5:42, 15:37; 27, 1:33, 11:29, 21:24; 28, 7:20, 17:15; 29, 3:11,
13:07, 23:02; 30, 8:58, 18:53.
May 1, 4:49, 14:44; 2, 0:40, 10:36, 20:31; 3, 6:27, 16:22; 4,
2:18, 12:14, 22:09; 5, 8:05, 8:00; 6, 3:56, 13:51, 23:47; 7, 9:43,
19:38; 8, 5:34, 15:29; 9, 1:25, 11:21, 21:16; 10, 7:12, 17:07;
11, 3:03, 12:59, 22:54; 12, 8:50, 18:45; 13, 4:41, 14:37; 14,
0:32, 10:28, 20:23; 15, 6:19, 16:14; 16, 2:10, 12:06, 22:01; 17,
7:57, 17:52; 18, 3:48, 13:44, 23:39; 19, 9:35, 19:30; 20, 5:26,
15:22; 21, 1:17, 11:13, 21:08; 22, 7:04, 17:00; 23, 2:55, 12:51,

Jupiter's Moons
Jupiter at opposition means the planet is at its boldest and
brightest for the year, but so too are its Galilean moons. With
close observing and the right equipment, you can detect differences in their sizes and colors (Io gives itself away with
its orange-yellow appearance, Ganymede is the largest of the
four). At opposition, Europa will appear the smallest, with
a diameter of 1.0″. Io will show at 1.1″, Callisto at 1.5″, and
Ganymede will boast a whopping 1.7″ diameter. Yes, these are
tiny differences, but after
enough repeat visits to the
quartet, you'll be able to
distinguish them from one
another with ease.
If you need help, use
the diagram on page 50 to
identify Jupiter's moons
at any date and time. All
of the May interactions
between Jupiter and its
satellites and their shadows
are tabulated on page 50.
Take the time to make
p Using a 1-meter Ritchey-Chrétien
a sketch, keeping in mind
telescope, Damian Peach captured
that a polished drawing
the shadow of Ganymede (top left)
isn't necessarily the goal.
as it traveled across the face of
Rather, it's the process
Jupiter in March 2017. Golden Io
of looking while you're
gleams to the right of the planet.
s k y a n d t e l e s c o p e . c o m * M AY 2 0 1 8

49
http://www.skyandtelescope.com
Sky and Telescope - May 2018

Table of Contents for the Digital Edition of Sky and Telescope - May 2018
