Stars 44 Oph and λ Sqr in early evening lunar occultations, Oct. 20-21

Around the onset of nautical twilight in the U.K., the waxing crescent Moon occults naked-eye stars at similar times on consecutive evenings starting October 20. BAA graphic by Ade Ashford.
Around the onset of nautical twilight in the U.K., the waxing crescent Moon occults naked-eye stars at similar times on consecutive evenings, starting with magnitude +4.2 44 Ophiuchi on October 20 and concluding with magnitude +2.8 Lambda (λ) Sagittarii on October 21. While the graphic above shows the stars’ disappearance times for the centre of the British Isles, times for other locations around the U.K. are tabulated below. BAA graphic by Ade Ashford.

Magnitude +4.16 star 44 Ophiuchi, otherwise known as b Ophiuchi, lies 13 degrees east of Antares in Scorpius. The former is occulted at the dark limb of the 4½-day-old waxing crescent Moon between 18:06 and 18:18UT (7:06pm and 7:18pm BST) as seen from the British Isles on Tuesday, October 20. The occultation occurs when the Moon is about 6 degrees above the southwest horizon, so the reappearance of 44 Ophiuchi at the Moon’s bright limb is unobservable from the U.K.

Fast forward 24 hours and the by now 5½-day-old Moon lies very close to magnitude +2.82 star Lambda (λ) Sagittarii, otherwise known as Kaus Borealis, the tip of the ‘Teapot’ asterism’s ‘lid’ in Sagittarius. Depending on where you live in the British Isles, the star disappears at the dark lunar limb between 18:10 and 18:23UT (7:10pm and 7:23pm BST) on October 21.

Note that the Moon lies just 8 degrees high in the south-southwest at the disappearance of λ Sgr. If you have exceptionally clear skies, you might see the star’s reappearance at the bright limb approximately one hour later, but the setting Moon will be very low in the southwest.

Location Occultation disappearance
of 44 Oph, October 20 (UTC)
Occultation disappearance
of λ Sgr, October 21 (UTC)
Aberdeen 18h 09.9m 18h 17.1m
Armagh 18h 08.2m 18h 13.5m
Belfast 18h 08.7m 18h 14.3m
Birmingham 18h 14.7m 18h 19.6m
Cambridge 18h 16.9m 18h 21.8m
Cardiff 18h 14.2m 18h 18.5m
Carlisle 18h 11.4m 18h 17.4m
Cork 18h 08.1m 18h 11.9m
Douglas 18h 10.5m 18h 16.1m
Dublin 18h 09.4m 18h 14.3m
Edinburgh 18h 10.1m 18h 16.6m
Galway 18h 06.4m 18h 10.9m
Inverness 18h 07.7m 18h 14.9m
Kirkwall 18h 07.3m 18h 15.3m
Leeds 18h 13.7m 18h 19.3m
Lerwick 18h 07.6m 18h 16.1m
Liverpool 18h 12.8m 18h 18.0m
London 18h 17.3m 18h 21.9m
Newcastle 18h 12.5m 18h 18.7m
Norwich 18h 17.5m 18h 22.9m
Oban 18h 07.5m 18h 14.1m
Pembroke 18h 12.3m 18h 16.4m
Plymouth 18h 14.2m 18h 17.7m
Southampton 18h 16.7m 18h 20.8m

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