Sky and Telescope - April 2016 - 2

April 2016
On the cover:
The lunar surface's
low plains and rugged
highlands mostly
cluster in two diﬀerent hemispheres.
PHOTOCOMPOSITE:
BACKGROUND: TRENT M. HARE ET AL.
/ U.S. GEOLOGICAL SURVEY SCIENTIFIC
INVESTIGATIONS MAP 3316; MOON:
NASA GSFC / ARIZONA STATE UNIV.

F E AT U R E S

22

Mapping the Universe's
Ancient Sound Waves
Astronomers are combing through
the largest map of galaxies ever
created to ﬁnd the imprint of primordial sound waves.
By Daniel Eisenstein

28

Big Fish, Small Tackle
Grab your binoculars and drop a line
in the deep pool of the Virgo Galaxy
Cluster. By Mathew Wedel

34

Star Parties in
the 21st Century
Organized observing events have
undergone explosive growth since the
1980s. Here's why. By Rod Mollise

66

Choosing a Camera
for Astrophotography
The question isn't which is best,
but which is best for your goals.
By Richard S. Wright, Jr.

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Printed in the USA.

2

41 In This Section
42 April's Sky at a Glance
43 Binocular Highlight
By Gary Seronik

44 Planetary Almanac
45 Northern Hemisphere's Sky
By Fred Schaaf

Our Two-Faced Moon
Planetary scientists still don't know
why one side of Earth's satellite looks
so diﬀerent from the other.
By Paul Spudis

COVER
STORY

O B S E RV I N G A P R I L

April 2016 sky & telescope

46 Sun, Moon & Planets
By Fred Schaaf

48 Celestial Calendar
By Alan MacRobert

52 Exploring the Moon

S&T: RICHARD TRESCH FIENBERG

16

VOL. 131, NO. 4

34

By Charles A. Wood

54 Deep-Sky Wonders
By Sue French

There's more to find online @

SkyandTelescope.com

S &T T E S T R E P O R T

58 Starlight Xpress
Trius-SX814C CCD

ONLINE MARKETPLACE

By Johnny Horne

Browse personal used equipment and sell your own without
paying a fee.

ALSO IN THIS ISSUE

SkyandTelescope.com/marketplace

4 Spectrum
By Peter Tyson

6 Letters
8 75, 50 & 25 Years Ago
By Roger W. Sinnott

ASTRONOMY EVENTS

Check out our events calendar
for upcoming museum exhibits,
star parties, and more - or add
your own event to our listings!
SkyandTelescope.com/
astronomy-events

10 News Notes
57 Book Review
By Monica Young

62 New Product Showcase
64 Telescope Workshop
By Gary Seronik

72 Gallery
84 Focal Point
By Emily Lakdawalla

ONLINE STORE

Shop our online store for globes,
sky atlases, and more.
ShopatSky.com
ASTROPHOTO GALLERY

Enjoy readers' best images and
upload your own.
SkyandTelescope.com/gallery

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Sky and Telescope - April 2016

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