(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 04:55 and sets at 21:50
3rd & 4th pm Mercury passes to the S of M45 – The Pleiades.
9th pm Venus lies to the SW of M45 – The Pleiades.
28th pm Mercury lies less than a degree to the East of Venus.
Mercury has its best evening showing of the year and is at greatest eastern elongation on the 17th. It moves from Aries to Taurus during the month. It sets at 22:20 at the start of the month and by month’s end it sets at 22:45. It fades from mag -1.0 to mag +2.8 during the month.
Venus is visible in the evening sky, moving from Aries to Taurus during the month. At the start of the month, it sets at 21:40 and by month’s end it sets at 23:10. It maintains its brightness at mag -3.8 during the month.
Mars is visible in the evening sky, in Gemini during the month. At the start of the month, it rises during daylight hours and sets at 01:45, by month’s end it sets at 00:50. It fades from mag +1.6 to mag +1.7 during the month.
Jupiter is at western quadrature on the 21st and is visible in the morning sky in Aquarius during the month. At the start of the month, it rises at 04:05 and by month’s end, it rises at 02:15. It brightens from mag -2.1 to mag -2.3 during the month.
Saturn is at western quadrature on the 3rd and is visible in the morning sky in Capricornus during the month. At the start of the month, it rises at 03:35 and by month’s end, it rises at 01:40. It brightens from mag +0.7 to mag +0.6 during the month.
Uranus is not easily visible this month.
Neptune is not easily visible this month.
The last quarter moon is on the 3rd (20:50) with the new moon on the 11th (19:59). The first quarter moon is on the 19th (20:12). The full moon is on the 26th (12:14).
3rd am the 57% waning gibbous lies SW of Saturn at 04:00.
4th am the 47% waning crescent lies S of Saturn and SW of Jupiter at 04:00.
5th am the 36% waning crescent lies S of Jupiter at 05:00.
13th pm the 4% waxing crescent lies SE of Mercury and NE of Venus at 22:00.
14th pm the 8% waxing crescent lies NE of Mercury and SW of Mars at 23:00.
15th pm the 14% waxing crescent lies SW of Mars at 23:00.
16th pm the 22% waxing crescent lies NE of Mars at 23:00.
19th pm the 51% waxing gibbous lies N of Regulus (Alpha (α) Leonis, mag +1.4) at 23:00.
23rd pm the 91% waxing gibbous lies NE of Spica (Alpha (α) Virginis, mag +1.0) at 23:00.
26th pm the just past full moon lies NE of Antares (Alpha (α) Scorpii, mag +0.9) at 23:00.
31st am the 73% waning gibbous lies S of Saturn and SW of Jupiter at 03:00.
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.
There may be additional minor showers this month, details of which can be found in the below Information Sources and Links Section. 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.
There are no bright asteroids at opposition this month.
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. “If you want to have a safe gamble, bet on a horse – not a comet”, Dr Fred Whipple.
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.
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.
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.