10°CASSIOPEIAANDROMEDAPISCESARIESCETUSPERSEUSAURIGAPolarisCapella PleiadesAlgol
RadiantSeptember 9, 11 P.M.
Looking northeastEpsilon Perseid meteor showerMaginus and its sunrise rayWWW.ASTRONOMY.COM 37RISINGMOON
METEORWATCH
There should be a ray of hope
(OK, sunshine) spreading across
the floor of the battered crater
Maginus on the evening of
September 20. This 100-mile-
wide impact feature sports a
bulged-up floor, central moun-
tain peaks, and a low rim. The
last attribute is the most critical
for the crater’s appearance on
the 20th because it allows a
prominent V-shaped splay of
sunlight to reach across the
otherwise dark floor.
Like so many events in
astronomy, timing is everything
when it comes to seeing this ray.
On the evening before, Maginus
remains in complete darkness;
by the evening after, the Sun has
risen high enough to illuminate
nearly the entire crater. For the
best viewing, you might have towait until late evening when the
Moon dips low in the west. See
“Catch some Moon rays” in the
July Astronomy for more exam-
ples of sunrise and sunset rays.
Don’t confuse the Maginus
ray with the much more com-
mon ejecta rays best seen
around Full Moon. The latter
formed when large, relatively
recent impacts excavated
lighter-hued material and dis-
persed this debris in streaks
across the Moon’s face. The
most spectacular ejecta rays
spread from Maginus’ northern
neighbor, Tycho.
Maginus lies deep in the
Moon’s southern hemisphere
at a latitude of –50°. It appears
closer to the lunar limb than you
might expect, however, thanks
to the foreshortening effect ofthe globe curving away from us.
For the same reason, circular cra-
ters near the limb appear oval.
By the time Full Moon —
and a total eclipse — arrivesSeptember 27, the Sun lies high
in the lunar sky and shadows
have disappeared. All that
remains of Maginus are subtle
features for patient selenophiles.Because only a half dozen or so
major meteor showers occur each
year, observers often have to make
due with minor events. That is the
case in September. The best bet is
the Epsilon Perseids, which burst
on the scene with a slew of bright
meteors in 2008 and delivered a
similar display in 2013. In other
years, however, the rate tops out
at five meteors per hour.
The “shooting stars” appear to
radiate from a point in Perseus
near 2nd-magnitude Algol. For
North American observers, the
peak arrives the evening of
September 9, though Perseus
climbs highest just before dawn. A
thin waning crescent Moon, which
rises around 4 A.M. local daylight
time, won’t interfere at all.Lunar ray of a different stripe
A Perseus show two months in a row?
— Continued on page 42Epsilon Perseid meteors
Active Dates: September 5–21
Peak: September 9
Moon at peak: Waning crescent
Maximum rate at peak:
5 meteors/hourobservers. The ringed planet
stands nearly 20° above the
southwestern horizon as dark-
ness falls in mid-September
and doesn’t set until 10 p.m.
local daylight time. A waxing
crescent Moon points the way
September 18 when it passes
3° north of Saturn.
At magnitude 0.6, the
planet stands out against the
backdrop of eastern Libra.
Saturn’s only rival in this area
is magnitude 1.1 Antares,
located 12° to the southeast
in neighboring Scorpius.
The ringed world appears
best through a telescope when
it lies higher in the sky during
the early evening hours. Any
instrument will show the
planet’s 16"-diameter globe
surrounded by a ring system
that spans 37" and tilts 24° to
our line of sight.
You also should see Titan
in proximity to Saturn. This
8th-magnitude moon passes
Viewers could see up to five meteors per hour emanating from the con-
stellation Perseus the night of September 9/10.A normally inconspicuous crater in the southern highlands, Maginus
comes alive at sunrise when a beam of light shines through its battered
eastern wall. THOMAS MCCAGUE; INSET: NASA/GSFC/ASUOn the night of September 27/28, observers across the Americas
will see a 72-minute total eclipse of the Moon.OBSERVING
HIGHLIGHTNERayALL ILLUSTRATIONS:ASTRONOMY: ROEN KELLYMaginus