SkyEye

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

September 2009

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	Tue	Light-polluted skies don't help the poorly-observed Alpha Aurigids.
2	Wed
3	Thu	What happened to Jupiter's Galilean satellites?
4	Fri	Earth passes through Saturn's ring plane.
4	Fri	Full Moon
5	Sat
6	Sun
7	Mon
8	Tue
9	Wed
10	Thu	Moon occults the Pleiades: visible from about 1330 UT in the Philippine Sea.
11	Fri
12	Sat	Last Quarter Moon
13	Sun	Moon occults the Mars: visible from about 1500 UT from northwestern Russia.
14	Mon
15	Tue
16	Wed	Moon at perigee
17	Thu	Uranus at opposition
17	Thu	Saturn at conjunction
18	Fri	New Moon
19	Sat
20	Sun	Mercury at inferior conjunction
21	Mon
22	Tue	Equinox on Earth
23	Wed
24	Thu	Moon occults Antares during daylight hours.
25	Fri
26	Sat	First Quarter Moon
27	Sun
28	Mon	Moon at apogee
29	Tue	Like the earlier meteor shower, moonlight does the Delta Aurigids no favours.
30	Wed

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 towards the Earth early this month. An equinox occurs on Earth on 22 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: Virgo -> Leo
This elusive planet soon disppears into the sunset twilight when looked at from the northern hemisphere but from southern latitudes it appears quite high in the west before plummeting towards the horizon and disappearing by mid-month. It is at inferior conjunction on 20 September and reappears at the end of the month in the east just before sunrise.
Venus: Cancer -> Leo
The "morning star" is best seen from northern latitudes this month, high above the eastern horizon before sunrise. It is much closer to the horizon as viewed from the southern hemisphere and slowly losing altitude.
Mars: Gemini
The red planet is now rising around midnight. It is slowly brightening as it heads towards opposition early next year. It is occulted by the Moon on 13 September.
Jupiter: Capricornus
At least one of Jupiter's Galilean satellites is usually visible through a small telescope but not on 3 September. From about 0430 UT and lasting for approximately two hours, all four of this gas giant's largest satellites will either be in front of the planet, behind the planet or in its shadow, rendering them invisible. Jupiter was at opposition just last month so it is up most of the night, setting just before dawn.
Saturn: Leo -> Virgo
On 4 September, the rings will appear edge-on from Earth. This is known as a ring-plane crossing. Unfortunately, Saturn is far too close to the Sun to easily observe this phenomenon and conjunction occurs less than two weeks later.
Uranus: Pisces
At opposition on 17 September, this gas giant is up all night. It is just visible to the naked eye if the skies are very dark.
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 view of Saturn from its satellite Iapetus and is courtesy of NASA/JPL/Space Science Institute. Of all the major satellites of Saturn, Iapetus is the only one with a significant orbital inclination. Thus, whilst the rings appear nearly edge-on from all of the other major satellites, from Iapetus they are usually seen at a tilt. This image was taken during the Cassini-Huygens mission on 10 September 2007 and consists of 15 red, green and blue spectral filter images.