Sky and Telescope - March 2016 - 49

Learn how to use detailed star charts to find the faintest things
with your telescope: skypub.com/charts.

and brain. And instead of stacking these
best instants digitally, your mind has to
build up an impression the best it can
using only brain-quality memory. Still, as
Robert Burnham, Jr. famously wrote in his
Celestial Handbook, "there is no privilege
like that of being allowed to stand in the
presence of the original."
What can you see of Jupiter with
your scope? Of course it depends on the
scope's size and optical quality, but also
on the quality of the seeing and the longterm development of your own observing
skill. So don't think you've reached your
limits anytime soon.
Here are things to look for on Jupiter
in rough order from easy to hard -
depending, of course, on what the planet
is actually displaying when you look.
Belts and zones. Belts are dark, zones
are bright. The most prominent ones that
are usually present are labeled at far left.
(We show south up to match the view in
many scopes.) The nomenclature extends
to finer gradations, but fine belts and
zones not only come and go, they move
up and down a bit. So assigning names
such as "North North Temperate Belt"
versus "North North North Temperate
Belt" becomes anyone's judgment call.
Even a 60-mm scope will usually
show the two equatorial belts. Examine
them for whatever difference you can see
between them: width, darkness, color,
irregularities.
Belt irregularities. The details most
readily visible on Jupiter are often irregularities in edges of the equatorial belts.
Jupiter's rotation. If you can see
any such discrete details, you can detect
Jupiter's rapid rotation in less than 10
minutes of watching. Features rotate
from celestial east ("following," f ) to west
("preceding," p ). It takes 50 minutes for
a feature to rotate from Jupiter's central
meridian halfway to the preceding limb.
Limb darkening. Sunlight near the
planet's edges lights Jupiter's cloudtops
at a low angle, and our own line of sight
goes through thicker atmosphere there
before reaching the cloudtops. So Jupiter
is dimmer near the limb. This is especially obvious in photos. Around opposi-

tion, the limb darkening is uniform. At
other times, the side of Jupiter farthest
from the Sun in our sky is darkened more.
The Great Red Spot (GRS) is currently quite a strong orange-pink and
much easier to see now than in the years
when my wife called it the "Great Cottage
Cheese Spot," when it was sometimes
hard to recognize in my 12.5-inch.
The Red Spot Hollow (RSH) is the
indentation in the South Equatorial Belt
where the Great Red Spot lives. Sometimes it's white, sometimes tan or gray,
sometimes hardly visible.
White ovals. These are especially common in the South Temperate Belt (STB).
Oval BA, "Red Spot Junior," is the
long-lived product of the merger of three
white ovals in the STB that had already
lasted for decades beforehand. It's very
pale tan; good luck.
Blue patches sometimes mark the
edges of the equatorial belts against the
Equatorial Zone. They seem to be areas
of clear atmosphere between the clouds,
blue for the same reason our own clear
sky is blue. But the color is subtle.
Festoons often extend from blue
patches into the Equatorial Zone, where
they're blown sideways like banners in
the wind.
The Equatorial Band is a thin, subtle
line that occasionally forms right along
the equator.
Red ovals are small but quite dark red.
Barges are also narrow and dark, but
they're elongated east-west into line segments. They're often very red.
White outbreaks. Tiny, bright-white
dots of fresh, upwelling material may
evolve within days into thin white diagonal streaks, and occasionally into massive
white turbulent areas extending far along
inside a belt.
And of course you'll occasionally see
the tiny black shadow of one of Jupiter's
four big Galilean moons. The moons
themselves are harder to see against Jupiter's face because of their lower contrast.
Callisto, with the darkest surface, is the
least difficult and in fact is easy to mistake for a shadow. See the timetable of the
March satellites events on page 51.

Alan MacRobert

Jupiter's Moons
Mar 1
2
3

EAST

WEST

4
5
6

Io

7
8
9
10

Ganymede

11
12
13

Callisto

14
15
16
17
18
19
20
21
22

Europa

23
24
25
26
27
28
29
30
31

The wavy lines represent Jupiter's four big satellites. The central
vertical band is Jupiter itself. Each gray or black horizontal band is
one day, from 0 h (upper edge of band) to 24h UT (GMT). UT dates
are at left. Slide a paper's edge down to your date and time, and
read across to see the satellites' positions east or west of Jupiter.


http://www.skypub.com/charts

Sky and Telescope - March 2016

Table of Contents for the Digital Edition of Sky and Telescope - March 2016

Contents
Sky and Telescope - March 2016 - Cover1
Sky and Telescope - March 2016 - Cover2
Sky and Telescope - March 2016 - 1
Sky and Telescope - March 2016 - Contents
Sky and Telescope - March 2016 - 3
Sky and Telescope - March 2016 - A
Sky and Telescope - March 2016 - B
Sky and Telescope - March 2016 - 4
Sky and Telescope - March 2016 - 5
Sky and Telescope - March 2016 - 6
Sky and Telescope - March 2016 - 7
Sky and Telescope - March 2016 - 8
Sky and Telescope - March 2016 - 9
Sky and Telescope - March 2016 - 10
Sky and Telescope - March 2016 - 11
Sky and Telescope - March 2016 - 12
Sky and Telescope - March 2016 - 13
Sky and Telescope - March 2016 - 14
Sky and Telescope - March 2016 - 15
Sky and Telescope - March 2016 - 16
Sky and Telescope - March 2016 - 17
Sky and Telescope - March 2016 - 18
Sky and Telescope - March 2016 - 19
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Sky and Telescope - March 2016 - 28
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Sky and Telescope - March 2016 - 30
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Sky and Telescope - March 2016 - 33
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Sky and Telescope - March 2016 - 35
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Sky and Telescope - March 2016 - 48
Sky and Telescope - March 2016 - 49
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Sky and Telescope - March 2016 - Cover3
Sky and Telescope - March 2016 - Cover4
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