Sky and Telescope - April 2015 - 48

OBSERVING

Sun, Moon & Planets

Encounter at Aldebaran
Venus takes us on a grand tour of Taurus.
On April 4th, western North America, the
Paciﬁc, and eastern Asia experience a total
lunar eclipse with a total stage that lasts
around 10 minutes. Most of the rest of
North America can view the partial phases
as dawn brightens; see page 50.
April features up to ﬁve bright planets
in the evening hours. Venus dominates
the western sky for several hours after
sunset. Mercury appears low in twilight
after mid-month, and for a few days, acts
as a guide to ﬁnding dim Mars near it.
Jupiter shines prominently high in the
south at dusk. Saturn rises in the southeast in the late evening and is highest
before dawn.

DUSK AND EVENING
Venus shines at magnitude -4.1 for most
of April and continues to brighten. This
yellow-white beacon climbs a little higher

with each passing week for viewers at midnorthern latitudes, eventually appearing
more than a third of the way up the western sky at sunset. It stays up long after
dark; the interval between sunset and
Venus-set increases from about 3 hours
to 3½ hours during April as seen from
around latitude 40° north.
Especially lovely this month is Venus
passing by the Pleiades, the Hyades, and
Aldebaran. Venus starts April some 12°
below the Pleiades; it shines only 2° or
3° to their left by the 11th and 12th, and
about 7° upper right of Aldebaran on April
19th. Then, on April 20th and 21st, the
crescent Moon joins Venus, Aldebaran,
and the bright Taurus clusters in beautiful
arrangements. By month's end, Venus is
nearing Beta Tauri (Elnath).
Telescopes show the angular diameter
of Venus grow from less than 14″ to more

April 2-5

than 16″ tall in April, while its gibbous
phase shrinks from 78% to 68% sunlit.
Mercury is at superior conjunction
with the Sun on April 10th, but moves
rapidly out into the evening sky - far to
the lower right of Venus - in the following three weeks. By April 19th, Mercury,
shining at magnitude -1.4, should be
visible to the unaided eye (with diﬃculty)
very low in the west-northwest about 45
minutes after sunset. That same night,
look also for an extremely thin crescent
Moon, hardly more than 1 day old for
North America, less than a ﬁst-width at
arm's length to the left of, and slightly
higher than, Mercury.
Mars, much fainter at magnitude +1.4,
is ﬁnally sinking down into the sunset
after eight months of hanging ﬁre. Binoculars or a telescope show it just a few
degrees to the upper left of brighter Mer-

Dusk, April 19 -21

April 11

shortly after dark

45 minutes after sunset

shortly after dark

Moon
Apr 2

10°

VIRGO
Moon
Apr 21
Moon
Apr 3

Venus

10°

Aldebaran

Aldebaran

Hyades
CORVUS

Venus

Spica

April 2015 sky & telescope

Pleiades

Mercury moves
higher and closer
to faint Mars during
this 3-day period.

Moon
Apr 5

48

Hyades
Moon
Apr 20

Moon
Apr 4

Looking East-Southeast

Pleiades

Moon
Apr 19

Looking West

Looking West

Mars
Mercury
Sky and Telescope - April 2015

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