Sky and Telescope - June 2015 - 52

OBSERVING

Celestial Calendar

Jupiter's Moons
June 1
2
3

EAST

WEST

4
5
6

Ganymede

7
8

You may also notice Saturn's bright
surface through the Cassini Division
- as opposed to black sky in the parts
of the division oﬀ the planet's edge -
at times when a sunlit part of Saturn
appears through this narrow slot.
For several nights around Saturn's
May 22nd opposition, watch for the
Seeliger eﬀect: a slight brightening of the
rings with respect to the globe. This is
caused by the solid ice particles in the
rings backscattering sunlight more
eﬀectively than the cloudtops do.

9
10

Callisto

11
12

13
14
15

Europa

16
17

Moon Dance
In addition, Saturn and its rings are
surrounded by extra baubles: more
moons for amateur scopes than orbit
any other planet.
Even a 60-millimeter scope will usually reveal well-named Titan, half again
as big as our Moon. A 6-inch will show
the orange tint of Titan's thick photochemical smog, which hides this weird
world's rainclouds, rivers, and lakes of
liqueﬁed natural gas.

A SATURN GUID E
AT YO U R S C O PE
Our SaturnMoons app displays the
nine largest satellites at any time and
date, the rings' changing tilt, and
background info by J. Kelly Beatty.
Available from iTunes for $2.99.

A 4- or 6-inch scope will also show
Iapetus, Rhea, Dione, and (with a little
diﬃculty) Tethys. An 8-inch may occasionally catch fainter Enceladus closer
in. My 12.5-inch shows Enceladus pretty
regularly. You can identify the moons,
or ﬁnd exactly where to look for them,
at any time and date using the interactive tool at skypub.com/satmoons.
Or for handy use at the scope, get our
SaturnMoons app for phones and tablets as described above.
And of course, take every opportunity to show Saturn to others! Countless amateurs remember a ﬁrst view of
Saturn as the door that opened for them
the riches of astronomy.

18
19

Action at Jupiter

20
21

Mar 5

12:14

13:13

Mar 9

11:43

12:04

22
23
24
25
26
27
28
29
30
July 1

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 0h (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.

June 2015 sky & telescope

Jupiter sinks lower
in the western dusk in
June, so begin observing it with your scope as
soon as you can spot it
in twilight. Start from
brighter Venus to its
lower right. Jupiter is on
the far side of the Sun
from us, so it's near its
minimum apparent size;
it shrinks from 34″ to
33″ across its equator in
June. But it still shows
more illuminated area
than any other planet,

Last March, a month past opposition, Jupiter's North and South Equatorial Belts were
nearly equal on the side away from the Great Red Spot, but somewhat dissimilar on the
Red Spot's side. South is up. The Moon casting its shadow in the bottom images is Io.
Christopher Go of Cebu City, Philippines, took these images as part of his long-term
monitoring of Jupiter. He uses a 14-inch Celestron Schmidt-Cassegrain scope with a Skyris 132M planetary video camera and de-rotates Jupiter before stacking frames.

http://www.skypub.com/satmoons

Sky and Telescope - June 2015

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