(Please note all times are ST and are based on an observing location of Belfast and covers the month of September)
At the start of the month, the Sun rises at 06:30 and sets at 20:15. By month's end, it rises at 07:25 and sets at 19:00.
6th am Neptune and Phi (φ) Aquarii, mag +4.2 – 38 arc seconds gap.
Mercury is at superior conjunction on the 4th and is not visible this month.
Venus is not visible this month.
Mars is at conjunction on the 2nd and is not visible this month.
Jupiter is at eastern quadrature on the 8th and is visible in the evening sky in Ophiuchus. At the start of the month, it sets at 23:10 and by month’s end, it sets at 21:30. It fades from mag -2.1 to mag -1.9 during the month.
Saturn is visible in the evening sky in Sagittarius. At the start of the month, it sets at 01:20 and by month’s end it sets at 23:20. It fades from mag +0.3 to mag +0.5 during the month.
Uranus is visible in the evening sky in Aries. At the start of the month, it rises at 21:40 and by month’s end it rises at 19:45. It maintains its brightness at mag +5.7 during the month.
Neptune is at opposition on the 10th and is visible in the evening sky in Aquarius. At the start of the month, it rises at 20:30 and by month’s end it rises during daylight hours. It maintains its brightness at mag +7.8 during the month.
The first quarter moon is on the 6th (04:10) with the full moon on the 14th (05:33). The last quarter moon is on the 22nd (03:41) with the new moon on the 28th (19:26).
5th pm the 47% waxing crescent lies N of Antares (Alpha (α) Scorpii, mag +0.9) and W of Jupiter at 21:00.
6th pm the 58% waxing gibbous lies NE of Jupiter at 21:00.
8th pm the 77% waxing gibbous lies E of Saturn at 22:00.
13th pm the full moon lies S of Neptune at 22:00.
17th pm the 88% waning gibbous lies S of Uranus at 22:00.
19th pm the 72% waning gibbous lies NW of Aldebaran (Alpha (α) Tauri, mag +0.9) and S of M45 – The Pleiades at 23:00.
20th pm the 62% waning gibbous lies E of Aldebaran (Alpha (α) Tauri, mag +0.9) at 23:00.
26th am the 10% waning crescent lies N of Regulus (Alpha (α) Leonis, mag +1.4) at 05:00.
The best time to observe meteor showers is when the moon is below the horizon; otherwise its bright glare limits the number you will see especially the fainter ones. Below is a guide to this month's showers.
There are no bright meteor showers this month.
There may be additional minor showers this month, details of which can be found in the below Information Sources and Links Section.
Asteroid (135) Hertha is at opposition during daylight hours on the 6th at mag +9.6 in Aquarius. It will be visible from 22:00 on the nights of the 5th/6th and 6th/7th.
Asteroid (21) Lutetia is at opposition on the morning of the 28th at mag +9.4 near the Cetus/Pisces boundary. It will be visible from 22:00 on the evening of the 27th.
Finder charts and further information about other fainter asteroids can be found in the below Information Sources and Links Section.
Comet C/2018 W2 (Africano) is currently mag +11 and brightening. It is predicted to peak at mag +8 in September. It is at perihelion on the 5th and is at its brightest on the 25th. It will be visible all night during the month. It starts the month in Perseus before heading into Andromeda around the 9th, then into Pegasus around the 25th and then into Pisces around the 29th. It passes by several stars during the month:
3rd pm Gamma (γ) Persei, mag +2.9, 5th pm Tau (τ) Persei, mag +3.9, 14th pm Chi (χ) Andromedae, mag +5.2, 19th pm Mirach (Beta (β) Andromedae, mag +2.1), 21st pm Delta (δ) and Epsilon (ε) Andromedae, mag +3.3 and +4.4 respectively, 25th am Chi (χ) Pegasi, mag +4.8, 26th pm Algenib (Gamma (γ) Pegasi, mag +2.8) and 30th am Omicron (ο) Piscium, mag +4.3.
Finder charts and further information about the above and other fainter comets can be found in the below Information Sources and Links Section. Any of the above estimates are based on current information at the time of writing the guide and can be wrong - “Comets are like cats; they have tails, and they do precisely what they want”, David H Levy.
On the deep sky front this month, galaxies M81 and M82 can be observed in Ursa Major. 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 - NGC 869 and 884. In Triangulum, there is the galaxy M33. Finally Auriga is reappearing with its three open clusters M36, M37 and M38 as is Taurus with the excellent Pleiades - M45 and the Hyades.
Always keep an eye out for Aurorae. The autumn equinox is on the 23rd which sees the end of summer and the beginning of autumn. This is the day where the length of day and night is the same and after this the night will take over cumulating with the shortest day of the year on the winter solstice in December. 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. A new appendix has been added explaining some of the more technical terms used in the guide.
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.