SkyEye

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

April 2007

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	Sun
2	Mon	Full Moon
3	Tue	Moon at apogee
4	Wed	Comet 96P/Machholz 1 at perhihelion
5	Thu
6	Fri
7	Sat	Moon occults first-magnitude star Antares: visible from southeast Australia and New Zealand
8	Sun
9	Mon	3 Juno at opposition
10	Tue	Last Quarter Moon
11	Wed
12	Thu
13	Fri
14	Sat	Moon occults Mars: visible from India and southeast Asia
14	Sat	Moon occults Uranus: visible from eastern Russia, Japan, Alaska and northern Canada
15	Sun
16	Mon
17	Tue	New Moon at perigee: very high tides expected
18	Wed
19	Thu	Comet 2P/Encke at perhihelion
20	Fri
21	Sat
22	Sun	Dark skies after midnight aid viewing the Lyrid meteor shower
23	Mon
24	Tue	First Quarter Moon
24	Tue	This is not an outstanding year to watch the Pi Puppid meteor shower because of the lightness of the sky
25	Wed	Moon occults Saturn: visible from eastern Russia, Alaska and northwestern Canada
26	Thu	Moon occults first-magnitude star Regulus: visible from Alaska, northwestern Canada and the northwestern United States
27	Fri
28	Sat
29	Sun
30	Mon	A cross-quarter day occurs midway between equinoxes and solstices.
30	Mon	Moon at apogee

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 are not so constrained, often moving far above or below the ecliptic.

Sun: Pisces -> Aries
Comet 2P/Encke: Aries -> Cetus
This comet was first discovered in 1786 by Pierre Méchain. It was re-discovered in 1795 by Caroline Herschel, sister of William Herschel. Jean Louis Pons discovered this comet twice, once in 1805 and again in 1818. However, it was J.F. Encke who first recognized that all of these comets were in fact the same object; hence, this comet bears his name. Arriving every 3.3 years, this comet has the shortest known period. It may reach fourth magnitude at perihelion. Be very careful when observing comets near the Sun!
Comet 96P/Machholz 1: Cetus -> Pisces -> Pegasus
Discovered in 1986 by Don Machholz, this comet has an orbital period of 5.24 years. This is its fifth visit to the inner solar system since its discovery. It may reach second magnitude at perihelion. Be very careful when observing comets near the Sun!
Mercury: Aquarius -> Pisces -> Cetus -> Pisces -> Aries
For southern hemisphere observers, Mercury begins quite high in dawn skies but it soon heads for the horizon. The smallest planet in the solar system is at conjunction next month so it disappears from pre-sunrise skies by late April.
Venus: Aries -> Taurus
The "evening star" is dazzling viewers in the northern hemisphere as it hovers far above the sunset horizon. It continues to climb away from the Sun, rising ever higher in the darkening sky.
Mars: Capricornus -> Aquarius
The red planet is occulted by the Moon on 14 April and nears Uranus at the end of the month. It rises just ahead of twilight and is slowly brightening in the early morning sky.
3 Juno: Virgo
A small telescope is necessary to see this tenth-magnitude object at opposition on 9 April.
Jupiter: Ophiuchus
The largest planet in the solar system rises well before midnight.
Saturn: Leo
Setting in the west just as Mars rises in the east, the ringed planet is well-placed for observing in the pre-midnight hours of darkness.
Uranus: Aquarius
This distant gas giant rises at about the same time as Mars and the two planets appear very close in the sky at the end of the month.
Neptune: Capricornus
A small telescope is necessary to view the most distant planet in the solar system. It rises just as Saturn sets so may be difficult to spot in the morning twilight.

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 at Furman University.

The image of Hoag's Object in the SkyEye banner is courtesy of NASA and the Hubble Heritage Team (STScI/AURA). Discovered in 1950 by astronomer Art Hoag, this unusual ring galaxy is slightly larger than our own Milky Way. The blue ring is dominated by young, massive stars whilst the nucleus is comprised largely of older, yellower stars. Located 600 million light years away in the constellation of Serpens, Hoag's Object was photographed by the Hubble Space Telescope on 9 July 2001.