(Please note all times are ST and are based on an observing location of Belfast and covers the month of May)
At the start of the month, the Sun rises at 05:45 and sets at 21:00. By month's end, it rises at 05:00 and sets at 21:45.
Mercury is at superior conjunction on the 21st and becomes visible in the evening sky at month’s end when it sets at 22:55 in Taurus. It is mag -1.1 at month’s end.
Venus is a morning object this month but is not easily visible.
Mars is visible in the evening sky during the month, moving from Taurus to Gemini. It fades from mag +1.6 to mag +1.8 during the month. It sets around 00:05 by month’s end.
Jupiter is visible this month in Ophiuchus. It becomes a late evening object by month’s end. At the start of the month, it rises at 00:45 and by month’s end, it rises at 22:30. It brightens from mag -2.3 to mag -2.4 during the month.
Saturn is visible in the morning sky this month in Sagittarius. At the start of the month, it rises at 02:35 and by month’s end it rises at 00:35. It brightens from mag +0.5 to mag +0.3 during the month.
Uranus is a morning object this month but is not easily visible.
Neptune is not easily visible for most of the month. It rises at 02:45 in Aquarius by month’s end when it is mag +7.9.
Ceres is at opposition on the morning of the 29th at mag +7.0 in Ophiuchus. It is visible from 23:00 on the evening of the 28th.
The new moon is on the 4th (23:45) with the first quarter moon on the 12th (02:12). The full moon is on the 18th (22:11) with the last quarter moon on the 26th (17:33).
7th pm the 10% waxing crescent lies S of Mars at 23:00.
12th pm the 60% waxing gibbous lies NE of Regulus (Alpha (α) Leonis, mag +1.4) at 23:00.
16th pm the 95% waxing gibbous lies NE of Spica (Alpha (α) Virginis, mag +1.0) at 23:00.
20th am the 99% waning gibbous lies NE of Antares (Alpha (α) Scorpii, mag +0.9) and NW of Jupiter at 00:00.
21st am the 95% waning gibbous lies E of Jupiter at 0:00.
23rd am the 82% waning gibbous lies SE of Saturn at 02:00.
28th am the 37% waning crescent lies SE of Neptune at 04:00.
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.
The Eta Aquarids peak on the morning of the 6th with a theoretical ZHR of 50. However the radiant only rises in the morning twilight shortly before sunrise on the morning of the 6th from Ireland. This leads to a very short observing window with a much reduced ZHR given the very low radiant. The moon will not interfere this year with observations of the shower with new moon only occurring on the 4th.
There may be additional minor showers this month, details of which can be found in the below Information Sources and Links Section.
Asteroid (8) Flora is at opposition in the morning of the 12th at mag +9.7 in Libra. It is visible from 23:00 on the evening of the 11th.
Asteroid (14) Parthenope is at opposition during daytime on the 14th at mag +9.5 in Libra. It is visible from 23:00, on the nights of the 13th/14th and 14th/15th.
Asteroid (20) Massalia is at opposition during daytime on the 20th at mag +9.7 in Libra. It is visible from 23:00, on the nights of the 19th/20th and 20th/21st.
Finder charts and further information about other fainter asteroids can be found in the below Information Sources and Links Section.
There are no bright comets visible this month.
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 Leo, we have several galaxies on view including The Leo Triplet - M65, M66 and NGC 3628. M95, M96 and M105 can also be observed in Leo. The place to really find galaxies is in Virgo. The Virgo Super Cluster can be found here with numerous galaxies on view. Also in Virgo, M104 - the Sombrero Galaxy can be found. In Coma Berenices, there is M64 - the Black-Eye Galaxy. Also 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. Finally there are some excellent open clusters in Cancer - M44 - The Beehive Cluster and M67.
Always keep an eye out for Aurorae. The night sky does not get fully dark this month. Between mid-May and the early 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 May. Look to the North-West for a white/silvery glow 1.5 - 2 hours after sunset and to the North-East a similar amount of time before sunrise. 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.
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.