See a lunar occultation bonanza on the night of 5—6 November

By Ade Ashford

Observers in the British Isles should look low in the eastern sky shortly before 7pm GMT on 5 November to see the rising 16-day-old Moon glide in front of magnitude +3.7 gamma (γ) Tauri, a naked-eye star at the point of the V-shaped Hyades star cluster. As seen from the heart of the UK, γ Tauri (aka Hyadum I) disappears at the bright lunar limb at 6:59pm, reappearing at the Moon’s darkened waning gibbous limb at 7:51pm. See the article below for times at other locations. This is a simulated erect image view where east is left and north is up. All times given are GMT. AN graphic by Ade Ashford.

While many will be looking skyward to see terrestrial pyrotechnics this Bonfire Night, if you own a small telescope and can escape the light pollution, you can catch a glimpse of the rising 16-day-old waning gibbous Moon as it slides over magnitude +3.7 star gamma (γ) Tauri in the early evening of Sunday, 5 November. This is the prelude to a night of lunar occultations in the constellation of Taurus, culminating in first-magnitude star Aldebaran in the small hours of Monday morning.

As seen from London the times of gamma (γ) Tauri’s disappearance and reappearance are 6:55pm and 7:47pm, respectively. For observers north of the border close to Edinburgh, the star disappears at 7:02pm (though both the Moon and the star will be low in the east-northeast) and reappears at 7:54pm. For help in where to recover gamma (γ) Tauri, the star reappears close in line with 132 km-wide crater Langrenus as shown in the illustration above.

The next conspicuous naked-eye star in Taurus to be hidden by the Moon this night is Theta11) Tauri, but not everyone in the British Isles will see it. This magnitude +3.8 star only disappears behind the southern limb of the Moon for observers north of a line drawn between Liverpool and Scarborough. (All of Ireland and Scotland will see the event, weather permitting.) Anyone just south of the Liverpool—Scarborough ‘graze line’ will see a near miss. As seen from Edinburgh, θ1 Tauri disappears behind the Moon at 10:56pm and reappears at 11:24pm, while residents of Dublin will see the star hidden at 10:54pm, reappearing at 11:13pm.

Finally, the lunar occultation highlight for those prepared to stay up onto the small hours of Monday, 6 November is that of Aldebaran, the brightest star in the constellation of Taurus, at 2:30am as seen from the centre of the British Isles. The first-magnitude star reappears at the dark lunar limb at 3:25am. For London, the disappearance and reappearance times are 2:39am and 3:24am, respectively. As seen from Edinburgh, Aldebaran is hidden by the Moon at 2:27am and pops back into view shortly before 3:26am. All times quoted in this article are Greenwich Mean Time (GMT).

As with all occultation observations, to ensure success make sure that you are ready at the eyepiece of your telescope a few minutes before the appointed times. The Moon’s motion against the background stars is never more evident than when an occultation is about to occur — or more spectacularly, when a bright star reappears at the Moon’s dark limb.