September 2021 – What’s Up!
Week of 27th September
- Astronomical twilight ends at 20:45 BST at the start of the week and at 20:31 BST by the end of the week
- Saturn (+0.5) and Jupiter (-2.7) continue to dominate our southern night sky and are perfectly placed for observation this week. Watch the transit of Jupiter’s moon, Io and its shadow on Wednesday evening; the transit commences at 18:55 BST and finishes at 21:15 BST
- The Moon is Last Quarter on Wednesday
- The Sun currently has 2 active regions: AR2871 and AR2872. The sunspot number is 38
- The ISS makes multiple visible evening passes this week as follows:
Monday: 20:51, W to S, max 73°
Tuesday: 20:03, W to ESE, max 86° & 21:40, W, max 20°
Wednesday: 19:16, W to E, max 87° & 20:53, W to SSW, max 44°
Thursday: 20:06, W to SE, max 58° & 21:43, W to WSW, max 12°
Friday: 19:18, W to ESE, max 73° & 20:55, W to SSW, max 23°
Saturday: 20:08, W to SSE, max 32°
Sunday: 19:21, W to SE, max 43° & 20:59, WSW to SSW, max 11°
Week of 20th September
- Astronomical twilight ends at 21:03 BST at the start of the week and at 20:48 BST by the end of the week
- The Autumn Equinox occurs on Wednesday. At 20:21 BST the Sun will cross the Celestial Equator, heading south. This marks the start of autumn here in the Northern Hemisphere. There will be almost exactly 12 hours of night and day across our planet
- It is currently possible to spot five planets: Venus (mag -4.1) is setting low in our western evening sky, Saturn (+0.4) and Jupiter (-2.8) are high through the night, transiting at around 22:00 BST, Neptune (+7.8) follows further east and Uranus (+5.7) rises at 20:24 BST. For a sixth solar system planet, look to your feet to add Earth to the list!
- The Moon is Full on Tuesday – the Harvest Moon
- The Sun currently has 1 active region: AR2871. The sunspot number is 11
- The ISS makes multiple visible evening passes this week as follows:
Monday: 19:54, SW to E, max 31° & 21:30, WSW, max 49°
Tuesday: 20:43, WSW to E, max 72° & 22:20, W, max 14°
Wednesday: 19:56, WSW to E, max 58° & 21:33, W, max 44°
Thursday: 20:46, W to E, max 87° & 22:23, W, max 12°
Friday: 19:59, WSW to E, max 86° & 21:36, W, max 35°
Saturday: 20:49, W to E, max 87°
Sunday: 20:02, W to E, max 84° & 21:39, W, max 27°
Week of 13th September
- Astronomical twilight ends at 21:22 BST at the start of the week and at 21:06 BST by the end of the week
- Neptune reaches opposition on Tuesday, when it will be opposite the Sun as seen from Earth. It will be best placed for observation, appearing at its brightest, though still faint at mag +7.8, so binoculars or a telescope will be needed to see the planet. Look southeast in the constellation of Aquarius through the evening
- Saturn (mag +0.4) and Jupiter (-2.8) continue to dominate our evening skies. They will be joined by the waxing Gibbous Moon towards the end of the week
- The Moon is First Quarter on Monday
- The Sun currently has 5 active regions: AR2863, AR2864, AR2866, AR2868 and AR2869. The sunspot number is 93
- The ISS makes multiple visible evening passes this week as follows:
Thursday: 21:27, SW to SSW, max 14°
Friday: 20:41, SSW to SSE, max 23°
Saturday: 19:57, S to ESE, max 17° & 21:32, WSW to SW, max 31°
Sunday: 20:47, SW to ESE, max 46°
Week of 6th September
- Astronomical twilight ends at 21:42 BST at the start of the week and at 21:25 BST by the end of the week
- On Thursday evening, spot the 3 day old waxing Crescent Moon just under 7° from Venus (mag -4.1) as they set in the West. Look just after sunset, which is at 19:34 BST
- Jupiter (-2.8) and Saturn (+0.3) are well placed in our evening skies
- With little to no moonlight, this week is the perfect opportunity to observe M27, the Dumbbell Nebula, a planetary nebula in the constellation of Vulpecula, just below Cygnus. At mag +7 and only 8 arcminutes in size, you will need a good pair of binoculars or a telescope to find it
- The Moon is New on Tuesday
- The Sun currently has 5 active regions, AR2863, AR2864, AR2865, AR2866 and AR2867. The sunspot number is 68
- There are no visible evening ISS passes this week
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