SkyEye

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

September 2011

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	Thu	The nearly new Moon should not interfere with observations of the Alpha Aurigids (theoretical peak activity: about 13:00 UT).
2	Fri
3	Sat	Mercury at greatest elongation west
4	Sun	First Quarter Moon
5	Mon
6	Tue
7	Wed
8	Thu
9	Fri
10	Sat
11	Sun
12	Mon	The Full Moon nearest to the equinox this month is traditionally known as the "Harvest Moon".
13	Tue
14	Wed
15	Thu	Moon at apogee
16	Fri	1 Ceres at opposition
17	Sat
18	Sun
19	Mon
20	Tue	Last Quarter Moon
21	Wed
22	Thu
23	Fri	Equinox on Earth
24	Sat
25	Sun
26	Mon	Uranus at opposition
27	Tue	New Moon
28	Wed	Moon at perigee: with only 14 hours separating New Moon and perigee, expect unusually high tides.
28	Wed	Mercury at superior conjunction
29	Thu
30	Fri

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
Best seen in the dawn sky early in the month, Mercury reaches maximum elongation west on 3 September. However, it dives back towards the horizon and is soon lost to view as it undergoes superior conjunction on 28 September.
Venus: Leo » Virgo
The "evening star" is quite low above the western horizon after sunset but is slowly gaining altitude.
Mars: Gemini » Cancer
The red planet doesn't rise until after midnight. It approaches M44 (the Beehive Cluster) towards the end of the month.
1 Ceres: Cetus » Aquarius
Binoculars or a small telescope will be necessary to see 1 Ceres at opposition since it attains only eighth magnitude.
Jupiter: Aries
Rising as the Sun sets, the largest planet in the solar system is on display most of the night.
Saturn: Virgo
Saturn is getting increasingly difficult to see in the west at sunset as it approaches conjunction next month.
Uranus: Pisces
Uranus is at its brightest this month as it achieves opposition on 26 September.
Neptune: Aquarius
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.

The SkyEye banner features the beautiful planetary nebula NGC 2818. A planetary nebula is a glowing shell of gas surrounding a dying star. When a star begins to run out of fuel and expands into a red giant, the outer layers of the star are expelled into space, enriching the surrounding area with the heavy elements manufactured by the parent star. The remaining hot stellar core ionises the ejecta, causing it to glow for a few tens of thousands of years. Eventually the star fades away and nebula is no longer visible. This image was taken by the Hubble Space Telescope in November 2008 and is courtesy NASA, ESA, and the Hubble Heritage Team (STScI/AURA). The red colour represents nitrogen, green represents hydrogen and blue represents oxygen.