July 2021 – What’s Up!

Week of 26th July

  • Astronomical twilight ends at 00:15 BST at the start of the week and at 23:42 BST by the end of the week
  • Look out for the waning Gibbous Moon in close proximity to Jupiter (mag -2.8) on Monday evening in the southeast
  • The delta Aquarid meteor shower is active this week, with its peak on Wednesday. The bright Moon will reduce visibility to all but the brightest meteors. The shower has a max ZHR of 25 and its progenitor is comet P/2008 Y12 (SOHO)
  • The Moon is Last Quarter on Saturday
  • The Sun currently has two active regions, AR 2846 and 2847. The sunspot number is 35
  • The ISS makes multiple evening passes this week as follows:
    Monday: 22:55, W to SW, max 33°
    Tuesday: 22:08, W to SE, max 45° and 23:46, WSW to SW, max 11°
    Wednesday: 22:58, W to SSW, max 17°
    Thursday: 22:10, W to SSE, max 24°

Week of 19th July

  • Astronomical darkness returns this week as astronomical twilight ends at 00:55 BST on Wednesday and at 00:21 BST by the end of the week
  • Venus (mag -3.9) and Mars (+1.8) are both visible in our evening sky throughout this week; look low to the western horizon just after sunset
  • The Full Moon makes a close approach to Saturn (+0.2) on Saturday and Jupiter (-2.8) on Sunday. Look to the southeastern horizon to find the gas giants at around 23:00 BST
  • The Moon is Full on Saturday – the Buck Moon, also known as the Hay Moon and the Thunder Moon
  • The Sun currently has four active regions, AR 2842 in the northern hemisphere and 2843, 2844 & 2845 in the southern hemisphere. AR 2844 is a particularly rare high-latitude active region. The sunspot number is 53
  • The ISS makes multiple evening passes this week as follows:
    Monday: 21:59, WSW to E, max 72° and 23:36, W to E, max 86°
    Tuesday: 22:49, W to E, max 84°
    Wednesday: 22:01, W to E, max 87° and 23:38, W to ESE, max 75°
    Thursday: 22:51, W to ESE, max 87°
    Friday: 22:04, W to E, max 86° and 23:40, W to S, max 45°
    Saturday: 22:53, W to SE, max 60°
    Sunday: 22:06, W to ESE, max 74° and 23:43, W to SW, max 24°

Week of 12th July

  • Astronomical twilight does not end until 00:55 BST on 21st July
  • On Monday, the shadow of Jupiter’s moon, Callisto, will transit the planet’s disk. The transit starts at 22:48 BST, before Jupiter rises at 22:55 BST, and ends at 03:32 BST.  The shadow will be visible just above the Great Red Spot
  • Mercury is at its highest altitude in the morning sky on Tuesday. It rises at 03:43 BST, with sunrise at 05:05 BST. The planet (mag -0.4) will be 19° from the Sun and will reach a maximum visible altitude of 11°
  • Tuesday’s evening sky features Venus (mag -3.9) and Mars (+1.8) making a close approach to each other. They will appear with just 29 arcminutes of separation. Look to the western horizon soon after sunset (21:19 BST)
  • On Friday night it will be possible to spot the clair-obscur effects that produce the Lunar ‘V’ and ‘X’ at the Moon’s terminator. Look at around 22:45 BST with binoculars as the Moon approaches the western horizon
  • The Moon is First Quarter on Saturday
  • The Sun currently has two active regions, AR 2841 and AR 2842. The sunspot number is 24
  • The ISS makes multiple evening passes this week as follows:
    Monday: 22:41, S to ESE, max 16°
    Tuesday: 23:29, SW to E, max 42°
    Wednesday: 22:42, SSW to E, max 31°
    Thursday: 23:31, WSW to E, max 71°
    Friday: 22:44, WSW to E, max 56°
    Saturday: 21:57, SW to E, max 42° and 23:34, W to E, max 87°
    Sunday: 22:46, WSW to E, max 84°

Week of 5th July

  • Astronomical twilight does not end until 00:55 BST on 21st July
  • The Earth reaches aphelion on Monday, when it will be at its most distant point from the Sun in its annual orbit. There will be 1.02 AU or 152,100,527 km, between the Earth and the Sun
  • Venus (mag -3.9) and Mars (1.8) continue to feature in our evening sky. Look just a few degrees above the western horizon after sunset at around 21:30 BST to find the pair
  • The waning Moon means dark skies this week, the perfect time to search in and around the Summer Triangle for fainter objects such as M57, the Ring Nebula in Lyra. Binoculars or a telescope will be required
  • The Moon is New on Saturday
  • The Sun currently has four active regions, AR 2835, AR 2386, AR 2387 and AR 2388. The sunspot number is 81
  • The ISS returns to our evening sky this week with one visible pass:
    Sunday: 23:31, ESE to E, max 18°
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