September 2026 – What’s Up!

Week of 28th September

• Astronomical Twilight ends at 20:44 BST at the start of the week and at 20:29 BST by the end of the week.
• Saturn (+0.3) reaches opposition on Sunday, making it the best time of year to observe the ringed planet. It rises at around 18:45 BST through the week, transiting at around 01:00 BST. Saturn has 293 confirmed moons, how many can you spot?!
• This week the Deep Sky Challenge starts in Andromeda with the wonderful double star, Almach (+2.2). We then move a few degrees east to the open cluster Messier 34 (+5.2) in Perseus. We finish a few degrees further east with the variable star Algol, Beta Persei, which ranges in brightness from +2.1 to +3.4 as the primary star is eclipsed by the smaller secondary star. This happens roughly every three days and lasts for about ten hours – can you spot the variability? Use Almach as your comparison star.
• The Moon is Last Quarter on Saturday.
• The Sun currently has 7 active regions and the sunspot number is 88.
• There are multiple visible evening ISS passes this week (click here for full ISS pass details).

Week of 21st September

• Astronomical Twilight ends at 21:01 BST at the start of the week and at 20:46 BST by the end of the week.
• The September Equinox occurs at 01:08 BST on Wednesday, giving Earth equal length day and night. This marks the start of astronomical autumn for us in the northern hemisphere.
• Neptune (+7.8) reaches opposition on Saturday, though it will be trickier to spot than usual that day as the Full Moon will only be a few degrees away. Spot the Ice Giant on other evenings of the week as it rises at around 18:55 BST. Close by is Saturn (+0.3), which rises at around 19:17 BST this week. It is increasingly well placed for observation as it moves towards its opposition next week.
• With the waxing Moon, we turn our attention to open clusters this week, starting with Messier 39 (+4.6) in Cygnus, first spotted by Aristotle around 325BC! He thought it to be a comet. Then we move to Messier 52 (+6.9) in Cassiopeia, before moving on to NGC 457, the Owl Cluster (+6.4) just beside the W asterism of Cassiopeia.
• The Moon is Full on Saturday – the Harvest Moon.
• The Sun currently has 1 active region and the sunspot number is 11.
• There are multiple visible evening ISS passes this week (click here for full ISS pass details).

Week of 14th September

• Astronomical Twilight ends at 21:20 BST at the start of the week and at 21:04 BST by the end of the week.
• Saturn (+0.4) rises at around 20:00 BST this week and transits at around 02:25 BST, making it well placed for evening observing. Can you spot its brighter moons, such as Titan and Rhea?
• We return to the Summer Triangle for this week’s Deep Sky Challenge, making the most of this fascinating area of sky before it disappears. Start with the pair of planetary nebulae: M57, the Ring Nebula (+8.8) in Lyra and M27, the Dumbbell Nebula (+7.1) in Vulpecula, then enjoy the colours of Albireo (+5.1), the double star at the beak of Cygnus, the swan. Finish with the open cluster M29 (+6.6) at the centre of the Northern Cross in Cygnus.
• The Moon is First Quarter on Friday.
• The Sun currently has 6 active regions and the sunspot number is 77.
• There are multiple visible evening ISS passes this week (click here for full ISS pass details).

Week of 7th September

• Astronomical Twilight ends at 21:40 BST at the start of the week and at 21:23 BST by the end of the week.
• Uranus enters retrograde motion on Thursday. Normally the planets appear to be moving in an eastwards direction through the constellations, but on occasion, as the Earth overtakes a planet, it makes that planet appear to move in a westwards direction. Astrologers love a retrograde motion, it explains so much…!
• Saturn (+0.4) is the evening planet of the moment. It rises at 20:34 BST and is full of interest for the observer. Spot the planet in the eastern sky.
• With the dark skies of the New Moon, we can up the difficulty factor for this week’s Deep Sky Challenge. Start with the ‘easy’ galaxy, M31, the Andromeda Galaxy (+3.4) and its two satellite galaxies M32 (+8.1) and M110 (+8.1). We increase the difficulty as we move 14° to the south to find the Triangulum Galaxy (+5.7), hard to make out as it is quite diffuse. Finally, the difficulty is ramped up in the search for M74 (+9.4), a spiral galaxy in Pisces that has the lowest surface brightness of all the Messier objects. Good luck!
• The Moon is New on Friday.
• The Sun currently has 6 active regions and the sunspot number is 70.
• There are multiple visible evening ISS passes this week (click here for full ISS pass details).