The three top sights to observe or image this month
DON’T MISS: Partial Lunar Eclipse
BEST TIME TO SEE: 19 November from 06:00 UT until moonset
EQUIPMENT: Naked eye
To be ready for the partial lunar eclipse on the morning of 19 November, get up nice and early. Around 05:30 UT you’ll see a beautiful full Moon shining away above the western horizon. As time goes by and the Moon drops towards the horizon it’ll become eclipsed by Earth’s shadow, presenting what, it’s fair to say, is a tricky partial eclipse.
The background sky will technically still be astronomically dark at this time (the presence of that bright Moon and its reflected sunlight will have an effect of course, but that’s not a concern here), but as the Moon appears to drop towards the west-northwest horizon, dawn begins. As the sky lightens, the Moon remains visibleits brightness sustaining the view in the brightening morning twilight.
The Moon enters the weak outer part of Earth’s shadow, the penumbra, at 06:02 UT, but this is unlikely to be seen. As time advances, the Moon heads deeper into the penumbra, towards the darker umbral shadow. It reaches the umbral shadow at 07:19 UT and the period leading up to this will show the Moon’s northwest limb becoming darker as it enters the denser part of the penumbra. The umbra is more defined and a distinct shadow edge will start to appear after 07:19 UT, but the Moon’s low altitude and the brightening sky will make things tricky across the UK.
Eclipse magnitude is a measure of how much of the apparent diameter of the body being eclipsed is covered by the eclipsing entity. In this case the body being eclipsed is the Moon, the eclipsing entity is Earth’s shadow. The best views with the greatest magnitude percentages will be from locations further north and west within the UK. If we start with London, the umbra crossing starts just 6 minutes before moonset and the eclipse only reaches a maximum magnitude of 3 per cent before the Moon is lost below the horizon. In contrast, Stornoway on the Isle of Lewis experiences just over an hour of umbral shadow crossing, the partial reaching a peak magnitude of 74 per cent before moonset. From the west coast of Ireland the umbral eclipse begins an hour before moonset, the peak magnitude reaching 68 per cent. The eclipse reaches a magnitude of 18 per cent from the UK’s centre, where the Moon sets 20 minutes after the start of the umbral phase.
In order to see anything of this event, it’s essential to find a location where the horizon is clear, unobstructed and preferably flat in a west-northwest direction. A seaward horizon in this direction is perfect.
The Moon’s busy crescent phases
BEST TIME TO SEE: As specified
EQUIPMENT: Small/medium telescope
On 1 November, the 17%-lit waning crescent Moon shows favourable libration (a small apparent rocking and rolling motion) for a foreshortened view of the giant concentric region surrounding Mare Orientale on the Moon’s southwest limb. There’s another similar opportunity around 28 November too, at a greater phase and higher altitude. In the ensuing days the thinning waning crescent Moon presents some interesting opportunities. On 2 November, the 9%-lit waning crescent appears in the early morning sky along with mag. –0.8 Mercury. The bright inner planet will be located 4˚ from mag. +1.0 Spica (Alpha (α) Virginis).
A day later, on the morning of 3 November, the now 3%-lit lunar crescent lies 6˚ to the west-northwest (above and slightly right from the UK) of mag. –0.8 Mercury. This is a good opportunity to spot and identify this tricky planet if you’ve never seen it before.
Amazingly, if the sky is clear on the morning of 4 November the now ultra-thin lunar crescent may still be seen 7˚ below and to the left of Mercury as seen from the UK. This waning crescent will be less than 1%-lit and right on the theoretical threshold of visibility – so don’t expect this to be easy!
The evening reappearance of the Moon places it near to brilliant Venus on the evenings of 7 and 8 November. On the 7th, the 11%-lit waxing crescent Moon sits 7.2˚ to the west of mag. –4.4 Venus. Then, on 8 November the Moon, now 20%-lit, appears 6.6˚ to the east of Venus.
On the evening of 11 November, the first quarter Moon near to Jupiter (see below) will be exhibiting the clair-obscur effects known as the ‘Lunar X’ and ‘Lunar V’. Both lighting effects reach a peak around 23:30 UT, when the letters X and V will be visible on the lunar terminator with a telescope.
Jupiter moon events
BEST TIME TO SEE: As specified
EQUIPMENT: Small/medium telescope
As Jupiter drifts closer towards the evening twilight, there is still time for a few interesting events regarding its four largest moons. On 6 November there’s a great opportunity to see the outer Galilean moon, Callisto, transiting Jupiter’s disc. The event conveniently begins as darkness falls at around 16:45 UT, Callisto moving off Jupiter’s disc at 21:20 UT. Transits of Callisto only occur when viewing relatively close to a Jovian equinox, as occurred in May of this year.
On 9 November, there’s another conveniently timed event visible as the sky is darkening. A telescope will show the large dark shadow of Ganymede as it crosses the atmosphere of Jupiter.
This event plays out until 18:36 UT. However, if you miss this transit, there’s another opportunity to see Ganymede’s huge shadow in transit on 16 November. This particular event starts under dark-sky conditions, beginning at 19:08 UT and concluding at 22:36 UT.
For those without the aid of a telescope, there’s a wonderful meeting between the first quarter Moon and mag. –2.3 Jupiter on the evening of 11 November. At 21:45 UT, as the pair approach the southwest horizon prior to setting, they will be around 5˚ apart – that’s about 10 apparent Moon diameters.