SkyEye

Welcome to SkyEye, your guide to this month's celestial events.

April 2013

The Calendar

All times and dates are given in Universal Time (UT).
Nightly darkness estimates are calculated for 45° N and 30° S.
Like total solar eclipses, lunar occultation events can be seen only from limited regions on Earth (and sometimes not at all if the occultation takes place during daylight hours). However, the Moon will appear close in the sky to its 'target' for some hours either side of the actual occultation, regardless of where you are.

Date		Event
1	Mon
2	Tue
3	Wed	Last Quarter Moon
4	Thu
5	Fri
6	Sat
7	Sun
8	Mon
9	Tue
10	Wed	New Moon
11	Thu
12	Fri
13	Sat
14	Sun
15	Mon	Moon at apogee
16	Tue
17	Wed	Mars at solar conjunction
18	Thu	First Quarter Moon
19	Fri
20	Sat
21	Sun
22	Mon	Light from the waxing gibbous Moon may interfere with the Lyrids (theoretical peak activity: about 11:00 UT).
23	Tue	A relatively new shower (they've only been detected since 1972), the southern hemisphere's Pi Puppids (theoretical peak activity: 17:00 UT) are also washed out by moonlight.
24	Wed	The nearly-full Moon occults first-magnitude star Spica: visible from Brazil, southern Africa and Madagascar from about 22:15 UT.
25	Thu	The Full Moon is partially eclipsed by the Earth's shadow.
26	Fri
27	Sat	Moon at perigee
28	Sun	Saturn at opposition
29	Mon
30	Tue

Coming up next month...

Next month plays host to both an annular solar eclipse and a penumbral lunar eclipse.

The Solar System

The word planet is derived from the Greek word for 'wanderer'. Unlike the background stars, planets seem to move around the sky, keeping mostly to a narrow track called the ecliptic, the path of the Sun across the stars. Dwarf planets and small solar-system bodies including comets, are not so constrained, often moving far above or below the ecliptic.

Sun: Pisces » Aries
Mercury: Aquarius » Pisces » Cetus » Pisces
Observers in southern latitudes will find Mercury pleasingly high above the eastern horizon before sunrise for much of the month. The apparition for those in the northern hemisphere is much more disappointing, with the elusive planet difficult to find low in the sky. Look for the smallest planet in the solar system earlier rather than later in the month as it spends the entire time descending towards the Sun.
Venus: Pisces » Aries
The evening star is climbing slowly in the western sky after sunset but remains inconveniently close to the horizon for all terrestrial observers.
Mars: Pisces » Aries
The red planet is at solar conjunction on 17 April and is lost to view the entire month.
Jupiter: Taurus
Venus may be the evening star but it is the largest planet in the solar system that rules the skies before midnight. But don't wait too long to look for it as it is setting earlier every night.
Saturn: Libra
At opposition on 28 April, the ringed planet is up all night and well placed for observation.
Uranus: Pisces
At solar conjunction at the end of last month, this ice giant is still too near to the Sun to be visible.
Neptune: Aquarius
A small telescope is necessary to view the most distant planet in the solar system. It should be far enough removed from the solar glare to be visible in the early morning hours.

The Celestial Sphere

Constellations are patterns of stars in the sky. The International Astronomical Union (IAU) recognises 88 different constellations. The brightest stars as seen from the Earth are easy to spot but do you know their proper names? With a set of binoculars you can look for fainter objects such as nebulae and galaxies or some of the closest stars to the Sun.

Descriptions of the sky for observers in both the northern and southern hemispheres are available for the following times this month. Subtract one hour from your local time if summer (daylight savings) time is in effect.

Local Time	Northern Hemisphere	Southern Hemisphere
1730 hours (1830 hours summer time)	45° N	30° S
1930 hours (2030 hours summer time)	45° N	30° S
2130 hours (2230 hours summer time)	45° N	30° S
2330 hours (0030 hours summer time)	45° N	30° S
0130 hours (0230 hours summer time)	45° N	30° S
0330 hours (0430 hours summer time)	45° N	30° S
0530 hours (0630 hours summer time)	45° N	30° S

For More Information...

Consult our online glossary for non-technical explanations of many of the astronomical terms used in these pages.
Blue moons, eclipses, the dates of Easter and much more can be found at the Interactive Astronomy Pages.
For more information about the objects and events described in SkyEye, visit these astronomy-related sites.

Credits

Much of this information can be found in this month's issue of your favourite amateur astronomy magazine available in your local bookshop. Another excellent source is the current edition of the Astronomical Calendar by Guy Ottewell and published by the Universal Workshop.

The SkyEye banner features an image of Saturn captured by the spacecraft Cassini in early October 2004. This view of Saturn is impossible from Earth; only the spacecraft Voyager I, Voyager II and Cassini have seen the ringed planet in a gibbous phase. This picture is courtesy of NASA, the Jet Propulsion Laboratory and the Space Science Institute.