SkyEye

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

September 2010

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	Wed	Last Quarter Moon
1	Wed	Toward the end of the night, the Moon interferes with viewing the Alpha Aurigids.
2	Thu
3	Fri	Mercury at inferior conjunction
4	Sat
5	Sun
6	Mon
7	Tue
8	Wed	New Moon at perigee: expect particularly high tides since perigee occurs six hours after the new phase.
9	Thu
10	Fri
11	Sat	Moon occults Venus: daytime event.
12	Sun
13	Mon
14	Tue
15	Wed	First Quarter Moon
16	Thu
17	Fri
18	Sat	Second encounter in the triple conjunction of Jupiter and Uranus
19	Sun	Mercury at greatest elongation west
20	Mon
21	Tue	Apogee
		Jupiter at opposition
		Uranus at opposition
22	Wed
23	Thu	Equinox
23	Thu	This Full Moon is popularly known as the "Harvest Moon."
24	Fri
25	Sat
26	Sun
27	Mon
28	Tue	Moon occults the Pleiades: visible from around 04:20 UT in southern South America and the Falkland Islands.
29	Wed	The waning gibbous Moon interferes somewhat with observations of the poorly-understood Delta Aurigids.
30	Thu

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: Leo » Virgo
The solar north pole is most inclined toward the Earth early this month. An equinox occurs on Earth on 23 September. The word equinox means "equal night" so that on this day, the (centre of the) Sun spends an equal amount of time above and below the horizon everywhere on the planet.
Mercury: Leo » Sextans » Leo » Virgo
Inferior conjunction occurs on 3 September so Mercury is not visible early in the month. Unlike last month, the northern hemisphere gets the best views of this tiny planet when it appears in the east before sunrise from mid-month. Greatest elongation west is on 19 September, after which Mercury heads back toward the Sun.
Venus: Virgo » Libra
The "evening star" heads back toward the western horizon but is still quite high as seen from southern latitudes.
Mars: Virgo » Libra
Look for the red planet low in the west after sunset.
Jupiter: Pisces
The largest planet in the solar system is up all night, with opposition occurring on 21 September, just three days after its second encounter with Uranus.
Saturn: Virgo
Conjunction occurs next month so the ringed planet is getting quite low in the west at sunset.
Uranus: Pisces
Like Jupiter, this gas giant is at opposition on 21 September and is up all night. It is just visible to the naked eye if the skies are very dark. Look for it near brilliant Jupiter.
Neptune: Capricornus
A small telescope is necessary to view the most distant planet in the solar system. Opposition was last month so it sets only just before dawn.

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 SkyEye banner features a collision of galaxy clusters and is courtesy of NASA, ESA, CXC, M. Bradac (University of California, Santa Barbara) and S. Allen (Stanford University). When MACS J0025.4-1222 was formed, gravity caused the ordinary matter in the colliding galaxy clusters to slow down whereas the dark matter, which at best interacts only weakly with itself, continued on its original course. Thus, this object provides both confirmation of the existence of dark matter and a further understanding of its properties. This image is a composite of Hubble Space Telescope and Chandra X-ray Observatory data where dark matter is coloured blue (mapped by Hubble using gravitational lensing techniques) and ordinary matter is coloured pink (mapped by Chandra detecting X-rays from gas heated by the collision).