Home
Meetings Timetable
Club News
Observing & Equipment
This Months Sky Guide
Weather
Burren Starparty
Gallery
About The Club
Join / Contact Us
Links    

 
Talk Astronomy
on our Forum
Free to register! 

 

                  

THIS MONTHS SKY GUIDE 

The Sun

At the start of the month, the Sun rises at 05:35 and sets at 21:25. By the end of the month, it rises at 06:30 and sets at 20:20.

The Planets

Despite being low in the West, the movement of Venus, Mars and Saturn in August provides a good example of how the solar system is constantly in motion. On the evening of the 1st, the three planets form an isosceles triangle with Venus to the West of the other two. Saturn lies less than two degrees to the North of Mars.

By the evening of the 8th, Venus now sits three degrees to the South of Saturn with Mars to the East of Venus. By the evening of the 13th, Venus has moved further East and sits to the South-West of Mars with Saturn to the West of the two inner planets. In addition the waxing crescent moon joins the party on the evening of the 13th to the South-East of Mars.

By the evening of the 19th, Venus passes two degrees to the South of Mars with Saturn to the West of the two inner planets. MAKE SURE THAT THE SUN HAS SET BEFORE TRYING TO OBSERVE THIS.

Mercury is an evening object this month and is at greatest eastern elongation on the 7th; however it is poorly placed for observation. It is at its best at the very start of the month when it should be around mag +0.3, low in the West after sunset. MAKE SURE THAT THE SUN HAS SET BEFORE TRYING TO OBSERVE THIS.

Venus is at greatest eastern elongation on the 20th but is very low in the evening sky. This is due to the ecliptic lying at a low angle to the horizon. By month’s end, it sets less than an hour after the sun at 21:00. It brightens during the month from mag -4.2 to mag -4.4. It is involved in a celestial waltz with Mars and Saturn during the month and the details are above.

Mars is sinking towards the evening twilight and sets an hour after the sun at 21:20 by month’s end. It is involved in a celestial waltz with Venus and Saturn during the month and the details are above.

Jupiter rises at 22:50 at the start of the month and at 20:50 by month’s end. It is in Pisces, to the South of the Circlet asterism and brightens during the month from mag -2.7 to mag -2.9. The gap between Jupiter and Uranus is three degrees at the start of the month and falls to two degrees by month’s end. Currently its South Equatorial Belt has gone missing; also its four Galilean moons are worth a look in a small telescope.

Saturn is also sinking towards the evening twilight and sets less than an hour after the sun at 21:10 by month’s end. It is involved in a celestial waltz with Venus and Mars during the month and the details are above.

Uranus rises at 22:45 at the start of the month and at 20:45 by month’s end. It is in Pisces, to the South of the circlet asterism and brightens during the month from mag +5.8 to mag +5.7. The gap between Uranus and Jupiter narrows to two degrees during the month with Uranus lying to the West of Jupiter.

Neptune is at opposition on the 20th and moves into Aquarius from Capricornus. It rises at 21:50 at the start of the month and during daylight hours by month’s end. It maintains its brightness during the month at mag +7.8. At opposition it lies within three degrees to the North-West of Iota Aquarii (mag +4.3), within two degrees to the North-East of Mu Capricorni (mag +5.1) and four degrees to the North-East of Delta Capricorni (mag +2.9).

The Moon

The last quarter moon is on the 3rd with the new moon on the 10th. The first quarter moon is on the 16th with the full moon on the 24th.

On the morning of the 1st, the waning gibbous moon lies to the East of Jupiter and Uranus at around 01:00.

On the mornings of the 4th and 5th, the waning crescent moon lies near to M45 –The Pleiades. On the 4th, it lies to the North-West of the cluster and to its South-East on the 5th. On the morning of the 5th, it also lies to the North of Aldebaran (Alpha Tauri, mag +0.9). On both mornings look around 03:00.

On the morning of the 7th, the waning crescent moon lies less than two degrees to the South of M35, at around 04:00.

On the evening of the 14th, the waxing crescent moon lies to the South-East of Spica (Alpha Virginis, mag +1.0) at around 21:00.

On the evening of the 17th, the waxing gibbous moon lies less than two degrees to the North-West of Antares (Alpha Scorpii, mag +0.9), at around 22:00.

On the evening of the 23rd, the waxing gibbous moon lies to the North-West of Neptune at around 23:00.

On the evening of the 26th, the waning gibbous moon lies to the North of Jupiter and Uranus at around 23:00.

On the evening of the 31st, the waning gibbous moon lies less than two degrees to the South-West of M45 –The Pleiades at around 23:00.

Meteors

The ZHR or Zenithal Hourly Rate is the number of meteors an observer would see in one hour under a clear, dark sky with a limiting apparent magnitude of 6.5 and if the radiant of the shower were in the zenith. The rate that can effectively be seen is nearly always lower and decreases as the radiant is closer to the horizon. The Zenith is the overhead point in the sky for an observer. The radiant is the point in the sky, from which (to a planetary observer) meteors appear to originate, i.e. the Perseids, for example, are meteors which appear to come from a point within the constellation of Perseus. A fireball is defined by the International Astronomical Union as a meteor brighter than any of the planets, i.e. magnitude -4 or brighter. The International Meteor Organisation alternatively defines it as a meteor which would have a magnitude of -3 or brighter at the zenith.

The first shower of August is the Iota Aquarids which peak on the 6th with a ZHR of 2. The Northern Delta Aquarids also peak on the 6th with a ZHR of 10. The radiants are visible from midnight with little lunar interference from a waning crescent moon rising in Gemini at 01:55 on the morning of the 7th.

The major shower of the month is the Perseids which peak on the night of the 12th/morning of the 13th. The peak is predicted to fall between 00:30 and 03:00 on the morning of the 13th. The ZHR is 100 with typically fast (34 km/s) meteors and a good proportion of bright meteors leaving trains. The radiant is circumpolar and is visible once darkness falls. This is one of the best showers of the year and there is no lunar interference, so go and enjoy!

The final two showers in the month are in Cygnus. The first is the Kappa Cygnids which peak on the 18th with a ZHR of 3 and the possibility of slow fireballs. The second is the Alpha Cygnids which peak on the 21st with a ZHR of 5. Both radiants are circumpolar and become visible once darkness falls. For the Kappa peak, there may be some lunar interference in the first part of night with a waxing gibbous moon setting in Ophiuchus at 00:15 on the morning of the 19th. For the Alpha peak, there will be lunar interference with a bright waxing gibbous moon setting in Capricornus at 03:40 on the morning of the 22nd.

Comets

Comet 10P/Tempel 2 is predicted to be around mag +10 in August and fade slowly. It is heading South and can be located in Cetus. It moves into the tail of the sea monster, passing less than a degree to the East of Deneb Algenubi (Eta Ceti, mag +3.5) on the morning of the 5th. It is a morning comet and is visible from around 03:00 at the start of the month and from around 01:00 by month’s end to the South-East of Jupiter and Uranus.

Deep Sky

On the deep sky front this month, galaxies M81 and M82 can be observed in Ursa Major. Check out the constellation Canes Venatici with the globular cluster - M3 and several galaxies including M51 - the Whirlpool Galaxy and M63 - the Sunflower Galaxy. In Hercules, two globular clusters – M92 and the excellent M13 can be observed and in Lyra – M57 – The Ring Nebula can be observed. In Vulpecula – M27 – The Dumbbell Nebula can be found. In Andromeda, M31 – The Andromeda galaxy can be observed along with its satellite galaxies M32 and M110. In Perseus, there is the open cluster M34 and the excellent Double Cluster. Finally in Triangulum, there is the galaxy M33.


General Notes

Always keep an eye out for Aurorae. We have the return to dark skies in August with Astronomical twilight no longer dominating the night. Between May and the middle of August, Astronomical twilight is present at night. This is when the sun is between twelve and eighteen degrees below the horizon. This time of year is very good for observing the numerous satellites and other objects in orbit above us.

Watch out for NLCs - Noctilucent Clouds during August. They are mostly visible between the Northern latitudes of 50 to 65 degrees, however sightings have been made as far South as Iran – 38 degrees. Look to the North-West for a white/silvery glow with the best times between 22:30 and Midnight and between 02:00 and 03:30. They can sometimes be faint, sometimes bright. Other interesting naked eye phenomena to look out for include the Zodiacal Light and the Gegenschein. Both are caused by sunlight reflecting off dust particles which are present in the solar system.

The Zodiacal Light can be seen in the West after evening twilight has disappeared or in the East before the morning twilight. The best time of year to see the phenomenon is late-Feb to early-April in the evening sky and September/October in the morning sky - it's then that the ecliptic, along which the cone of the zodiacal light lies, is steepest in our skies. The Gegenschein can be seen in the area of the sky opposite the sun. To view either, you must get yourself to a very dark site to cut out the light pollution. When trying to observe either of these phenomena, it is best to do so when the moon is below the horizon.

Clear Skies
Neill McKeown

Information Sources Used and Links

www.skyviewcafe.com - Used for the Sun and Planets section. Also partly used for the Moon Section

Sky at Night Magazine Observing Guide and CD

www.aerith.net and http://cometchasing.skyhound.com – Used for the Comet Section for information and finder charts

http://www.ast.cam.ac.uk/%7Ejds/ - BAA and SPA Comet page

http://kometen.fg-vds.de/fgk_hpe.htm - German Comet page

http://www.rasnz.org.nz – Royal Astronomical Society of New Zealand website – good for asteroids

BAA Handbook

Stardust Magazine

Sky Guide 2010 – South Dublin Astronomical Society

Philip’s Stargazing 2010

Patrick Moore’s 2010 Yearbook of Astronomy

www.heavens-above.com – For the latest ISS passes, Iridium Flares and Shuttle launches

www.irishastronomy.org – Irish Federation of Astronomy Societies Website

www.stronge.org.uk – Excellent weather site including Space Weather

www.irishastro.org.uk – Irish Astronomical Association website

www.eaas.co.uk – Northern Ireland Amateur Astronomy Society

The latest astronomy news - brought to you by Astrowire.