Sky Notes March 2023
Director of Observations
Dundee Astronomical Society
From our Director of Observations, Brian Kelly.
THE SKY AT 9 PM GMT IN MID-MARCH
Observing the Moon Ken Kennedy
The map above shows the night sky as it will appear from central Scotland at the time and date shown. The point in the sky directly overhead is at the centre of the map; the outer circle is the horizon with the cardinal compass points in the direction shown.
The map shows the brighter stars that are visible to the unaided eye. Some of the more distinctive constellations are outlined.
March 1st sunrise 7.04 am GMT sunset 5.44 pm GMT
March 15th sunrise 6.28 am GMT sunset 6.14 pm GMT
March 31st sunrise 6.45 am BST sunset 7.48 pm BST
In mid-March, the sky is reasonably dark between 7.30 pm and 5.00 am GMT.
Monday March 20th is the Spring Equinox when the Sun crosses into the northern half of the sky, and spring officially begins in the northern hemisphere.
British Summer Time (BST) begins on Sunday March 26th; clocks should be put forward by one hour.
The Sun lies in the constellation of Aquarius for the first part of March, and then moves into neighbouring Pisces from Sunday 12th onwards.
The sunrise, sunset and twilight times given here are for Dundee but generally apply across central Scotland.
March begins with the Moon at wide gibbous phase, shining high in the south-east as the sky grows dark.
Full Moon is on Tuesday March 7th. That night, the Moon rises just north of east as the Sun sets and is in the south at midnight, below the figure of Leo the Lion. The Moon sets north of west soon after sunrise the following morning.
Late on the evenings of Thursday 9th and Friday 10th, the waning gibbous Moon lies near the bright star Spica in the constellation of Virgo.
Last Quarter is on the morning of Wednesday March 15th. The half-illuminated Moon rises in the early hours and is very low in the south at dawn.
The waning crescent Moon may just be spotted low above the south-east horizon for the next couple of mornings before it disappears into the bright dawn twilight.
New Moon is on the evening of Tuesday March 21st, and the very narrow young crescent might be seen low above the western horizon after sunset on Wednesday 22nd, when it will lie just below Jupiter; binoculars may be needed for this. The Moon will be easier to find on the following evening, Thursday 23rd, when it will be to the lower right of Venus.
On Friday 24th, the crescent Moon will appear immediately to the upper left of Venus, and on Tuesday 28th it will be just to the upper left of Mars.
First Quarter falls on Wednesday March 29th, when the half Moon will be very high in the south among the stars of Gemini as the sky grows dark.
March is the best month of the year for a high elevation Moon at around first quarter. The 1st March sees a 9.5 day old Moon transiting at an elevation of 61º at 20:11 UT. Going from North to South, Plato is not very far from the terminator so look for the rim shadows on the floor of the crater. The Montes Recti, or Straight Range, a 90 km long range of irregular ridges lies between Plato and the terminator and will be casting a dramatic shadow eastwards. Moving south over Mare Imbrium, you will see the Montes Carpatus at the south end of the mare with the great crater Copernicus to the immediate south. Close to the terminator much of the floor will be in shadow but you might just see the first light falling into the complex central peaks. You will also see the impressive terracing, at least on one inner side of the crater. Passing southwards, past the crater Reinhold and then the smaller area called Mare Cognitum, the next crater of note is Bullialdus, 61km in diameter and with classic well-formed terracing and a tight cluster of central peaks. The ejecta blanket is not particularly prominent which might suggest that the crater was formed by an impact strike close to vertical. South again and into the chaotic cratered highlands try to pick out Longomontanus, an ancient eroded crater 145km in diameter, then a short distance south, the distinctive shape of Clavius (231km) with the Porter (north) and Rutherford (south) breaching its walls. Libration in latitude is -5.5º so the south polar region is tipped towards us. Have a look along the southernmost limb and note any peaks which appear.
By 3rd March the Moon’s elevation has only decreased by 3º to 58º at transit, and still at the civilised hour of 21:51 UT. I have previously mentioned Mare Humorum and Gassendi and the terminator will just have cleared this area so another good opportunity of have a close look at the floor of Gassendi with its multiple central peaks and irregular floor with several rilles. For this sort of detail you will require stable air conditions and relatively high magnification. A bit further north you probably can’t miss the smaller crater, Kepler (32km), with its distinctive rather dense ray system. This is even more obvious near to full Moon. Just a bit north again and Aristarchus is just emerging from shadow. It might be worth staying up for a couple of hours to watch this brightest of craters slip into sunlight.
The Moon is full on the 7th March and has descended to a maximum elevation of 40º at transit. Following full Moon, elevation drops rapidly until on 15th March, when the Moon is at last quarter, it only reaches 5º and is effectively out of a realistic observational window. New Moon is on the 21st when the invisible Moon will have reached a transit elevation of 31º, so we, as observers, are in business again as the Moon moves towards first quarter. For a few days, although the Moon will be gaining elevation, it will be a slim crescent and will transit mid-afternoon and so not be available for several hours when it will have dropped lower in the sky.
By 19:00 UT on the 24th March, the 3.2 day old Moon will be towards the west at an elevation of about 28º. The terminator is well placed to show the craters Langrenus and Petavius. Look again at the complex central peak array of Petavius, and the fracture which runs along half of the floor and should be clearly seen at this phase. Also, with libration at +5.5º in longitude, you will be able to see Mare Smythii and Mare Marginis on the eastern limb.
2023 March 24. 3.2 days
The 29th March brings first quarter and an elevation at transit of 60º at 19:55 UT. Once again time to slowly move along the terminator and see the old favourites, from the north, Aristillus, Autolycus and Archimedes (just on the terminator) in Mare Imbrium. North past the Montes Apenninus with Rima Hyginus a bit to the east but still clearly seen, then on to the large, eroded craters Ptolemaeus and Alphonsus and, less eroded, Arzachel. From there move southwards and take in the array of so many craters of different sizes and ages right to the south polar region, exposed by a libration in latitude of -6º.
Mercury is at superior conjunction on the far side of the Sun on March 17th, and will be hidden in the Sun’s glare for much of the month. However it emerges into the evening sky in the last week of March, and by the end of the month will be setting in the west around an hour-and-a-half after the Sun.
Venus begins the month very close to Jupiter in the evening twilight. On Wednesday 1st, the two planets sit side-by-side just over half a degree - about one Moon-diameter - apart; by Thursday 2nd Venus will be around the same distance above Jupiter (see diagrams below). The two planets then draw further apart, Venus climbing higher while Jupiter sinks lower. By the end of March, Venus will be a dazzling object shining at magnitude -4.0 high in the west as the sky grows dark, setting almost four hours after the Sun.
Mars remains a bright orange ‘star’ in the evening sky, though it does continue to fade noticeably from magnitude 0.4 to 0.9 during the month. It also moves eastward, travelling from the upper left of Aldebaran in Taurus to lie near the feet of Gemini by the end of March.
Jupiter lies close to Venus at the start of March, but sinks lower and sets earlier as the month progresses. By the end of March it will be setting less than an hour after the Sun and all but lost in the twilight.
Saturn is rising just shortly before the Sun, and will remain hidden in the glow of dawn throughout March.
Uranus is in southern Aries, and sets late in the evening. Venus passes just over one degree from Uranus during the last few days of the month, but with the distant planet at magnitude 5.8, binoculars (and a clear western horizon) will be needed to observe this close approach.
Neptune is in conjunction with the Sun this month and won’t be visible.
Wednesday 1st March, 19:00UT Thursday 2nd March, 19:00UT
March is a month of changes in the sky; the winter constellations have slipped into the south-west, and the spring stars are now climbing higher in the south-east.
The hourglass outline of Orion the Hunter is dipping lower in the evenings, though you can still follow the line of his belt to the left towards Sirius, the Dog Star. Sirius appears to sparkle even more strongly as it approaches the horizon. To the upper right of Orion is the V-shaped head of Taurus the Bull and the star cluster of the Pleiades or Seven Sisters.
High above Orion is the bright star Capella, in the constellation of Auriga, and also the twin stars of Gemini, Castor and Pollux. Between Gemini and Sirius, to the left of Orion, is Procyon, the Little Dog Star.
Lower in the north-west are the stars of Perseus, the ‘W’ of Cassiopeia, and the faint outline of Cepheus. Just above the northern horizon are the bright stars Vega and Deneb, which rise into the north-east in the early hours of the morning.
The seven stars of the Plough are almost overhead, with the two ‘pointer’ stars showing the way to the Pole Star; the curve of the Plough’s handle leads down to the bright red giant star Arcturus in the east. Arcturus sits at the base of the kite-shaped constellation of Boötes the Herdsman. To the north-east of Boötes is the distinctive semi-circle of stars representing Corona Borealis, the Northern Crown.
High in the south-east is the distinctive shape of Leo the Lion, its head marked by the curve of stars known as the ‘Sickle’ with the star Regulus at the bottom. To the lower right of Regulus is a bright yellow star, Alphard, brightest star in the long and straggling constellation of Hydra, the many-headed serpent of mythology. Between Leo and Boötes, nearer the horizon, are the stars of the zodiacal constellation Virgo which form the pattern of a large and distorted ‘Y’..
The Milky Way appears as a faint band of light stretching from Deneb in the north, through Cassiopeia, Perseus and Auriga, into the south-west past Gemini and Orion. As we move into spring, the Milky Way sinks lower towards the west and becomes less prominent.