Partial lunar eclipse on 28th follows second encounter with Jupiter

Alan Pickup

Author: Alan Pickup

The maps show the sky at 23:00 BST on the 1st, 22:00 BST (21:00 GMT) on the 16th and at 20:00 GMT on the 31st. Summer time ends at 02:00 BST on the 29th when clocks are set back one hour to 01:00 GMT.

The month opens with an impressive conjunction between the Moon and Jupiter in the constellation Aries, the first of their two meetings this month. Jupiter stands 4°, or eight Moon-breadths, below-left of the Moon when then rise in the east during our evening twilight on the 1st. As they climb to pass high in the south in the early hours of the 2nd, the Moon’s easterly progress carries it 2.5° above Jupiter as viewed from Edinburgh.

Their second conjunction comes hours after a partial eclipse of the Moon on the evening of the 28th, visible in its entirety from Scotland as the Moon cuts through the northern part of the Earth’s shadow.

The event gets underway towards the end of our evening twilight at 19:02 BST on the 28th when the Moon is standing 12° high in the east as seen from Edinburgh, while Jupiter shines brightly 7° to its lower-left.  At that moment the eastern (lower-left) limb of the Moon begins to enter the penumbra, the shadow’s outermost region where the Sun’s light is partially obscured.

Little dimming may be noticed until the Moon nears the shadow’s central dark umbra where no direct sunlight penetrates. Between 20:35 and 21:53, the umbra takes a shallow bite out of the lower part of the Moon, amounting to only 6% in area at mid-eclipse. The eclipse is over when the Moon leaves the last of the penumbra at 23:26, by which time it is 44° high in Edinburgh’s south-east and 5° right of Jupiter. The Moon has moved to within 2.5° of Jupiter is it dips towards the western horizon at the end of that night.

This is not the only eclipse this month and not the most spectacular. Sadly, though, the annular eclipse of the Sun on the 14th is not visible at all from Europe. Observers along a path that slants south-eastwards across the western USA and onwards to Brazil see a so-called “ring of fire” because the Moon is too distant to fully hide the brilliant disk of the Sun. Most of the rest of North and South America enjoy a partial solar eclipse.

As the Sun sinks another 11° southwards in October, Edinburgh’s sunrise/sunset times change from 07:15/18:49 BST (06:15/17:49 GMT) on the 1st to 05:15/16:37 GMT on the 30th, after our Summer Time ends on the morning of the 29th. The Moon reaches last quarter on the 6th, new during the annular eclipse on the 14th, first quarter on the 22nd and is full (and partially eclipsed) on the 28th. As the one following our Harvest Moon, the latter is also titled the Hunter’s Moon.

Recent image of Jupiter 2023-09-29 by Mark Phillips from Edinburgh

When Jupiter stands alongside the Moon on the 1st, a telescope shows the cloud-banded disk of the planet to be 48 arcseconds wide, with all four of its main moons lined up to its east and west. October sees it brighten from magnitude -2.8 to -2.9 as it draws closer to opposition on 3 November.

Uranus is 8° east of Jupiter and, at magnitude 5.7, is best seen through binoculars after the Moon has left the scene. A similar angle takes us to the Pleiades star cluster in Taurus the Bull which sits 4° left of the Moon on the evening of the 2nd.

The Moon’s continuing motion eastwards carries it through Gemini and Cancer to Leo where it shines as a 19% illuminated crescent above the brilliant planet Venus in our morning sky on the 10th.

Venus. which rises at Edinburgh’s east-north-eastern horizon at 03:04 BST on the 1st and in the east at 02:34 GMT on the 30th, climbs more than 30° into the south-east by sunrise. Dimming slightly from magnitude -4.5 to -4.3, it tracks from 7° west of Regulus through almost the full length of southern Leo. It passes 2.3° south of Regulus on the 10th, just as the Moon stands above them.

The planet shows a crescent through telescopes, 32 arcseconds in diameter and 37% sunlit on the 1st, though it shrinks to 22 arcseconds by the 30th when it is gibbous and 54% sunlit. Dichotomy, when (in theory, at least) it appears exactly D-shaped occurs on the 22nd, just a day before it lies furthest west of the Sun, 46°.

Mercury is bright at magnitude -1.0 but only 4° high one hour before sunrise on the 1st and is lost to the twilight within days. Mars remains hidden in the Sun’s glare.

Saturn 2023-09-12 Mark Phillips

Saturn fades a little between magnitude 0.5 to 0.7 but remains an obvious non-twinkling object in Aquarius in our evening sky. It moves from about 15° high in the south-south-east as darkness falls to pass 21° high in the south less than one hour before our map times and sets in the west-south-west after midnight. Look for it to the right of the Moon on the 24th when its disk is 18 arcseconds wide and its impressive ring system spans 41 arcseconds, with its north face tilted 10° earthwards.

Our charts have the Plough near its low-point in the north as the Square of Pegasus is high in the south. The oval glow of the galaxy M31 in Andromeda is even higher and further east, almost 45° above Jupiter whose motion slowly westwards against the stars of Aries is shown by an arrow. The asterism called the Circlet of Pisces sits under the Square and 5° or so above the most distant planet, Neptune. The latter’s magnitude 7.8 makes it barely visible through binoculars and demands a better chart than I can give here – the Web helps.

Vega, the leading star in the Summer Triangle it forms with Deneb and Altair, is now in the middle of our western sky while Taurus stands clear of the eastern horizon where Orion climbs into view a couple of hours later.

Swift meteors from the Orionids shower are visible almost month-long, their modest numbers perhaps highest on the morning of the 22nd, after the Moon has set. Originating as debris from Comet Halley, their paths diverge from a point above and left of Betelgeuse in Orion’s shoulder.

Comet Nishimura, mentioned here last time, became brighter than the 3rd magnitude as it swept within 34 million km of the Sun on 17 September. Its tail extends for several degrees in some images, but it never became the spectacular naked-eye object in the bright twilight that some had predicted. Other had claimed that it would disintegrate in the Sun’s heat, but this also didn’t happen.

Now tracking southwards from the Sun, C Nishimura is no longer visible from our latitudes and is fading sharply as it recedes, not to return until perhaps the year 2430. There are suggestions that the comet may be the parent of a minor meteor shower, the Sigma Hydrids, which peaks around 7 December from a radiant point to the south-east of Procyon. If so, the shower may be unusually active this year.

Diary for 2023 October

Times are BST

  • 2nd 04h Moon 3° N of Jupiter
  • 3rd 06h Moon 1.1° S of Pleiades
  • 4th 03h Moon 9° N of Aldebaran
  • 6th 15h Last quarter
  • 7th 12h Moon 1.4° S of Pollux
  • 8th 14h Moon 4°N of Praesepe
  • 10th 05h Venus 2.3° S of Regulus
  • 10th 10h Moon 4° N of Regulus
  • 10th 11h Moon 7° N of Venus
  • 14th 19h New Moon and annular solar eclipse
  • 20th 07h Mercury in superior conjunction on far side of Sun
  • 22nd 04h First quarter
  • 22nd     Peak of Orionids meteor shower
  • 24th 00h Venus furthest W of Sun (46°)
  • 24th 09h Moon 2.8° S of Saturn
  • 28th 21h Full Moon (Hunter’s Moon) and partial lunar eclipse
  • 29th 02h BST = 01h GMT End of British Summer Time
  • 29th 08h Moon 3° N of Jupiter
  • 30th 15h Moon 1.1° S of Pleiades
  • 31st 11h Moon 9° N of Aldebaran

This is an extended version, with added diary, of Alan’s article published in The Scotsman on 30 September 2023, with thanks to the newspaper for permission to republish here.