May 2025 – What’s Up!

Week of 26th May

• Astronomical twilight does not end until 21st July.
• Venus (-4.3) reaches Greatest Western Elongation on Sunday when it will be at its greatest apparent separation from the Sun. Look for the ‘morning star’ in the East in the hour before sunrise, which is at around 05:00 BST this week.
• As the Milky Way rises higher in the sky, so the concentration of Globular Clusters around the core of our galaxy becomes more visible. The southerly constellations of Serpens and Ophiuchus are rich with globulars, hunt down M5 (+5.7), M12 (+6.7), M10 (+6.6), M14 (+7.6), M107 (+7.9), and M9 (+7.7). All are between 14,000 and 30,000 light years from Earth.
• The Moon is New on Tuesday.
• The Sun currently has 8 active regions and the sunspot number is 105.
• There are no visible evening ISS passes this week (click here for full ISS pass details).

Week of 19th May

• Astronomical twilight ends at 00:15 BST at the start of the week and by Friday we will not see Astronomical darkness in Marlborough again until 21st July.
• As we lose astronomical darkness this week, attention is very much on the active Sun (safely, of course) and the chance of spotting noctilucent clouds; look to the north around sunset and sunrise for the best chance to catch this beautiful phenomenon.
• Mars (+1.2) is fading in our evening sky in the west, while Venus (-4.4) is climbing in the eastern morning sky.
• Hercules is home to three globular clusters: M13, the Great Hercules Cluster (+5.8), is a jewel of the summer sky, look a little further north to find M92 (+6.4) and the challenging NGC 6229 (+9.4).
• The Moon is Third Quarter on Thursday.
• The Sun currently has 4 active regions and the sunspot number is 58.
• There are multiple visible evening ISS passes this week (click here for full ISS pass details).

Week of 12th May

• Astronomical twilight ends at 23:43 BST at the start of the week and at 00:08 BST by the end of the week.
• Mars (+1.1) is the last of the planets in our evening sky, setting at 02:30 BST. Jupiter (-1.9) sets at around 23:30 BST, appearing very low to the western horizon in the hours after sunset. Venus (-4.5) rises at around 03:50 BST.
• Enjoy the last of astronomical darkness this week before it disappears for the summer from the 23rd.
• Three Globular Clusters to hunt down in the moonlight this week. Start with M53 (+7.6) in Coma Berenices, then head into Canes Venatici to find impressive M3 (+6.2), and end in Serpens with M5 (+5.6).
• The Moon is Full on Monday – the Flower Moon.
• The Sun currently has 5 active regions and the sunspot number is 70.
• There are multiple visible evening ISS passes this week (click here for full ISS pass details).

Week of 5th May

• Astronomical twilight ends at 23:15 BST at the start of the week and at 23:38 BST by the end of the week.
• It is the Equinox on Tuesday, but not on Earth… on Saturn! The Gas Giant’s ring system will be edge on as seen from Earth as the Sun crosses Saturn’s equator. Catch a glimpse of Saturn (+1.2) in the dawn sky about 6° to the west of Venus (-4.5).
• Jupiter (-2.0) is ever lower in our evening sky, now setting at around 23:45 BST.
• The Eta Aquariid meteor shower peaks on Tuesday with a nominal ZHR of around 40 meteors per hour. The shower’s progenitor is comet 1P/Halley.
• With the Moon in the bright Waxing Gibbous phase, spend some time exploring its surface with binoculars or a telescope this week. Enjoy sunrise over Sinus Iridum on Thursday evening.
• The Moon is Waxing Gibbous all week.
• The Sun currently has 4 active regions and the sunspot number is 77.
• There are multiple visible evening ISS passes this week (click here for full ISS pass details).