Sky and Telescope - August 2015 - 49

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

(in northern Perseus) rises high in the
sky. Or to say the same thing another
way, it's when the meteors hit your side of
the world most nearly head-on.
There's an added twist this year.
The Perseid meteoroids are little bits of
debris from Comet 109/P Swift-Tuttle,
which is on a 130-year orbit and last
passed through the inner solar system
in 1992. Meteor-stream modeler Jérémie
Vaubaillon ﬁnds that this year, Earth
should pass very close to the debris trail
that the comet shed during its return in
1862. This encounter will last for a few
hours centered on 18:39 UT August 12th.
Will there be an unscheduled outburst
of Perseids around then? The timing
favors observers in Asia. Meteor counters
on that side of the world are especially
needed to monitor what will happen.

Alex Conu assembled
this composite image
of six Perseids captured
near Ursa Major on
August 12, 2013, in the
Lotrului Mountains of
Romania. The lip of the
Big Dipper is under the
bear's ear; the handle-end
is at the tip of his tail.

How to Watch
It's easy just to be a Perseid spectator.
Many more people watch the shower now
than did a generation or two ago, especially families on rural vacations under
dark skies. In fact, America's national
parks are getting unprecedented numbers of people who say in surveys that a
dark, star-ﬁlled sky and genuine, natural
night are reasons why they visit. For this
we can credit the growing public awareness of light pollution (with big thanks to
the International Dark-Sky Association,
dark-sky.org) and the park system's own
management, which is recognizing and
working to preserve the parks' dark-sky
assets (S&T: May 2012, p. 26).
A Perseid watch goes best if you know
what you're doing. The later in the night
you go out the better. Let your eyes darkadapt, and plan to be patient. After midnight under a fairly rural sky you may see
a meteor a minute on average, but earlier
in the evening or under more ordinary
skies, your waits will be longer.
Dress warmly and wear a hat; the
cold under a clear sky late at night will
be more like October than August, and
you'll be lying still for a long time. Find
a spot in advance that has an open view
overhead and somewhat to the northeast,

Alan MacRobert

with no lights shining into the edge of
your vision. Bring a reclining lawn chair
and additional blankets or a sleeping bag.
The wraps are for both warmth and mosquito protection; bring repellent for parts
of you that are not covered.
Lie back and gaze into the darkest part
of the sky, probably straight overhead.
If much of the sky is dark, incline your
gaze somewhat toward the radiant in the
northeast. Many observers watch about
halfway from a shower's radiant to the
zenith. Relax and settle in.
On the other hand, some meteor
aﬁcionados plan to ﬂout the standard
wisdom and watch early in the evening.
At that time, when the radiant is still
low, the few Perseids that appear will be
spectacularly long Earthgrazers, skimming far across the sky along the top of
the atmosphere. For more about this facet
of meteor watching, pull out your August
2014 issue and turn to page 64.

Making a Count
If you have a fairly dark sky and an hour
or more to commit, why not try doing an
actual scientiﬁc meteor count? This way
you can help to determine the shower's
behavior this year, contributing to records
that will last for all time.
You'll need to follow the standard
procedures of the International Meteor
Organization, so that your count can
be analyzed to yield the shower's actual
strength - the standardized zenithal
hourly rate (ZHR) - during the time you
were watching. This way your count is

FOLLOW THE SHOWER ONLINE
As meteor watchers report their counts
to the IMO, you can watch this year's
Perseid activity curve develop hour by
hour at imo.net.

Sk yandTelescope.com August 2015

http://www.skypub.com/charts http://www.dark-sky.org http://www.imo.net http://www.SkyandTelescope.com

Sky and Telescope - August 2015

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