(Please note all times are ST unless otherwise stated and are based on an observing location of Belfast and covers the month of October)
At the start of the month, the Sun rises at 07:30 and sets at 19:00. By month's end, it rises at 07:25 UT and sets at 16:50 UT.
5th and 6th am Mars and Venus
Mercury is at superior conjunction on the 8th and is not visible this month.
Venus is a morning object this month. It rises at 05:00 at the start of the month, by month’s end it rises at 05:45 UT. It maintains it brightness at mag -3.8 during the month.
Mars is a morning object this month. It rises at around 05:20 at the start of the month, by month’s end it rises at 04:15 UT and maintains its brightness at mag +1.8 during the month.
Jupiter is at conjunction on the 26th and is not visible this month.
Saturn is visible this month in Ophiuchus. During the month, it is visible as soon as darkness falls and sets at 18:55 UT by month’s end. It maintains its brightness at mag +0.5 during the month.
Uranus is at opposition on the 19th and is visible in the evening sky this month in Pisces. At the start of the month, it rises at 19:30, by month’s end it rises during daylight hours. It maintains its brightness at mag +5.7 and lies near to Torcularis Septentrionalis (Omicron (ο) Piscium, mag +4.3) during the month.
Neptune is visible in the evening sky this month in Aquarius. During the month, it is visible as soon as darkness falls and sets at 01:50 UT by month’s end. It fades from mag +7.8 to mag +7.9 and lies near to Lambda (λ) Aquarii, mag +3.7 during the month.
The full moon is on the 5th (19:40). The last quarter moon is on the 12th (13:25) with the new moon on the 19th (20:12). The first quarter moon is on the 27th (23:22).
3rd pm the 95% waxing gibbous lies E of Neptune at 20:00.
6th pm the 98% waning gibbous lies S of Uranus at 21:00.
8th pm the 87% waning gibbous lies NW of Aldebaran (Alpha (α) Tauri, mag +0.9) and SW of M45 – The Pleiades at 22:00.
9th pm the 79% waning gibbous lies E of Aldebaran (Alpha (α) Tauri, mag +0.9) at 22:00.
15th am the 23% waning crescent lies NW of Regulus (Alpha (α) Leonis, mag +1.4) at 04:00.
17th am the 7% waning crescent lies N of Mars and NW of Venus at 07:00.
18th am the 3% waning crescent lies E of Venus at 07:00.
24th pm the 22% waxing crescent lies N of Saturn at 19:00.
30th pm the 77% waxing gibbous lies W of Neptune at 18:00 UT.
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.
The Orionids peak on the night of the 20th/21st with a ZHR of 15. The radiant rises at midnight and as new moon was the 19th, conditions are perfect for observing the shower this year.
There may be additional minor showers this month, details of which can be found in the below Information Sources and Links Section.
Asteroid (7) Iris is at opposition on the evening of the 30th in Aries. It is mag +6.9 and visible from 19:00 on the evening of the 30th.
Finder charts and further information about other fainter asteroids can be found in the below Information Sources and Links Section.
Comet C/2017 O1 (ASAS-SN) peaks around mag +7 in October and is currently mag +9. It is circumpolar during the month and is at perihelion on the 15th. It will start the month in Perseus, before moving into Camelopardalis. It passes to the W of 58 Persei, mag +4.3 around the 6th. It then passes to the W of 7 Camelopardalis, mag +4.4 around the 17th. Finally it passes to the W of Beta (β) Camelopardalis, mag +4.0 around the 23rd.
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 Lyra - M57 - The Ring Nebula can be observed and 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. Auriga reappears with its three open clusters M36, M37 and M38 as does Taurus with the excellent Pleiades - M45 and the Hyades. Orion returns to our skies with M42 - The Great Orion Nebula along with Gemini with the open cluster M35.
Always keep an eye out for Aurorae. On the morning of the 29th at 2am, the clocks go back one hour and summer time ends. 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.