Sky Notes February 2024
Director of Observations
Dundee Astronomical Society
From our Director of Observations, Brian Kelly.
THE SKY AT 9 PM GMT IN MID-FEBRUARY
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.
The sunrise, sunset and twilight times given here are for Dundee but generally apply across central Scotland.
OBSERVING THE MOON IN JANUARY
February 1st sunrise 8.09 am GMT sunset 4.41 pm GMT
February 15th sunrise 7.39 am GMT sunset 5.13 pm GMT
February 29th sunrise 7.05 am GMT sunset 5.44 pm GMT
In mid-February, the sky is reasonably dark between 6.30 pm and 6.15 am GMT.
The Sun lies among the stars of Capricornus for the first half of February, and then moves into Aquarius from Saturday 17th onwards.
February opens with the waning gibbous Moon rising in the south east in the early hours of the morning.
Last Quarter is late on the evening of Friday February 2nd; the half-illuminated Moon rises in the early morning of Saturday 3rd and is low in the south at the start of twilight. The waning crescent Moon may be followed into the dawn sky up until the morning of Tuesday 6th, when it will be low in the south-east about a hand-span to the right of the bright planet Venus.
New Moon is on Friday February 9th, and the young crescent Moon will reappear low in the south-west from Sunday 11th onwards.
On the evening of Wednesday 14th, the broad crescent Moon lies to the lower right of Jupiter; on the following evening, Thursday 15th, it will appear to the upper left of the planet.
First Quarter is on Friday February 16th. The half-Moon is high in the south as the sky grows dark, and during the evening will pass just below the star cluster of the Pleiades or Seven Sisters.
On the evening of Tuesday 20th, the gibbous Moon will lie to the lower left of the ‘Twin’ stars Castor and Pollux in the constellation of Gemini, and on Friday 23rd the Moon will sit just above the bright star Regulus in Leo.
Full Moon is on Saturday February 24th. The Moon rises in the east at sunset, and sets in the west shortly after sunrise the following morning.
Late on the evening of Wednesday 28th, the waning gibbous Moon will rise in the south-east to the lower left of the star Spica in Virgo.
February starts with the Moon at last quarter on the 2nd. From February into spring, last quarter Moon is at a low elevation in addition to being near transit in the early hours. For last quarter, the transit elevation is 16º at 05:28 UT. The Moon’s elevation falls to 5º when 25 days old, rising to 13º at New Moon on the 9th. By the 11th, the 2 day old Moon will appear low in the south-west as a thin crescent after sunset. By the 12th, the 3 day old moon will have risen considerably and will appear in the same area after sunset when the terminator will pass across the western side of Mare Crisium.
A 40º transit elevation on the 13th at 15:36 UT will mean that the Moon is higher still after sunset and may reward observation. Mare Crisium will be fully revealed and the small rayed crater Proclus, just outside the western rim on Mare Crisium will be seen close to the terminator. You should also be able to make out Mare Marginis and Mare Smythii on the limb to the east of Mare Crisium and the rather irregular Mare Undarum to its south-west. Further south, it’s a good phase to see Vallis Rheita which I have mentioned previously.
At almost 5 days on the 14th February, the Moon reaches 46o at transit at 16:25 UT. By 20:00 UT the terminator is gradually clearing Posidonius at the north-west side of Mare Serenitatis so a good time to watch for the rim of the flooded crater within Posidonius being revealed. It’s unlikely you will see the rilles on the floor as they will still be in part shadow. The basalt flooded crater Fracastorius in the north of Mare Nectaris is in a good position for examination.
By the 15th we are really getting to the point where the Moon is at a high elevation and ideal for detailed observation with high magnification if the air is reasonably still. The Moon at 6 days transits at 52o at 17:15 UT and the terminator passes through Mare Serenitatis, to the east of Mare Tranquilitatis and also east of Mare Nectaris where Rupes Altai curves to the south of the outstanding craters Catharina, Cyrillus and Theophilus.
At 7 days old on the 16th, the Moon is at a great elevation and phase to search along the terminator. Prime targets must be Rima Hyginus, situated in the north-east of Sinus Medii, and further south, the complex area around the craters Stofler, Faraday and Maurolycus.
By the 17th, the Moon has reached a transit elevation of 60º with the terminator running through Mare Imbrium and revealing the craters Archimedes, Autolycus and Aristillus. To the south-east of Archimedes is the Palus Putredinus which leads to Hadley Rille under the towering Mons Hadley, the area explored by David Scott and James Irwin of Apollo 15 in 1971. Further south, and west of the crater Thebit, the fault line of Rupes Recta is emerging from shadow and you should be able to see this later in the evening.
At 61º elevation at transit on the 18th, the Moon is perfectly placed at a civilised hour, so don’t waste the chance to explore if the sky is clear. Copernicus is emerging from shadow and it’s great to watch it do so over a few hours. Southwards and our favourites Tycho and Clavius are revealed for detailed examination. A bit further south yet and note a crater which always catches my eye – Moretus. Due to foreshortening it is seen as regularly elliptical but it is beautifully terraced with a distinct central peak. A libration of almost -6o reveals more detail around the south polar region so look for the far southern craters Short and Newton.
Still at very high elevation on the 19th, you will find the eastern end of Sinus Iridum emerging with the terminator passing west of Copernicus. Look again at the south polar area as more is revealed. Mare Humorum and Gassendi come into view on the 20th and north-west of Clavius, that oddly elongated crater Schiller. At 12 days old on the 21st, it’s the turn of Aristarchus, Herodotus and Vallis Schroteri, a great area to try sketching or imaging. As the Moon approaches full, there isn’t so much detail to see along the terminator but note the emergence of dark Grimaldi on the 22nd.
Full Moon is on the 24th February when its transit elevation has dropped to 44o. At any full Moon phase, take the time to look at the variation in colour, light and dark shading of the basalts in the maria which probably signify the various differentiated lava flows rich or poor in iron and titanium and possibly helpful, to a degree, in basaltic age estimations. The Moon is reasonably well placed over the next few days but its elevation rapidly decreases and observation times are later in the evening into the early hours. Because the Moon is losing elevation so rapidly, it is not so easy to observe in the early morning as it was two or three months ago.
By the last day of February, the 29th this year, the 20 day old Moon is only at an elevation of 17º and we will have to wait for the next lunation for further observational opportunities. February, March and April are by far the best months to see the Moon at a high elevation at civilised times. Given some clear weather there is so much to see and I would encourage any seasoned or potential Moon watchers to take every opportunity to observe, sketch or image and record what you see. I would recommend, for those interested, that you retain these notes as there will only be slight alterations to the date on which these features may again be seen in March and April. Any feedback of observations made will be very welcome at Society meetings.
Mercury is hidden in the bright glow of dawn during February, passing behind the Sun at superior conjunction on the 28th.
Venus rises about an hour-and-a-half before the Sun at the start of February, and may be spotted low in the south-east at dawn, shining at magnitude -3.9. It gradually sinks lower in the twilight and will be lost to view by the end of the month.
Mars is also rising just ahead the Sun but will remain invisible in the bright dawn sky. Jupiter shines brightly at magnitude -2.3 high in the south as the sky grows dark in the evening, and sets in the west around midnight at mid-month.
Saturn is low in the south-west in the early evening, setting around two hour after the Sun at the start of the month. However it will soon disappear from view as it approaches conjunction with the Sun on Wednesday 28th.
Uranus lies about 10o to the east of Jupiter, at magnitude 5.8.
Neptune is low in the south-west in the evening, setting around three hours after the Sun.
The giant figure of Orion the Hunter stands high in the south on February evenings, surrounded by the other brilliant stars of the winter sky. Orion’s left shoulder is represented by the red star Betelgeuse, and his right knee by blue-white Rigel. The distinctive line of stars marking Orion’s belt points upwards to the yellow star Aldebaran in the V-shaped head of Taurus the Bull; a little further along this line is the star cluster of the Pleiades or Seven Sisters.
Orion’s belt leads downwards to Sirius, or the Dog Star. At magnitude -1.4 this is the brightest star in the night sky, and although it is actually a white star, Sirius twinkles strongly, appearing to flash different colours as it does so.
The Square of Pegasus and the stars of Andromeda are now low in the south-west, with the ‘W’ of Cassiopeia just above. High overhead are the stars of Perseus and Auriga, along with the constellation of Gemini and its Twin stars Castor and Pollux. Below Gemini is the bright star Procyon, often known as the ‘Little Dog Star’.
Climbing higher in the east is Leo, with the bright star Regulus at the bottom of the ‘Sickle’ of stars representing the Lion’s head. Lower in the south-east is Alphard, brightest star in the constellation of Hydra the Water Snake. This long, straggling constellation is actually the largest in the sky, though most of its stars are rather faint and its outline difficult to follow. Yellow- coloured Alphard stands out in an otherwise barren area of sky; appropriately enough, its name means ‘the Solitary One’.
The seven stars of the Plough are high in the north-east, the two ‘pointer’ stars showing the way to the Pole Star. The curve of the Plough’s handle leads down to the red giant star Arcturus, low in the north-east. Two of the stars of the ‘Summer Triangle’, Deneb and Vega, remain visible all year round from Scotland, and on February evenings can be found low above the northern horizon.
The Milky Way continues to be well-placed in the sky during February, appearing as a faint band of light stretching from Deneb in the north-west, through Cassiopeia and Perseus, and into the south-east between Orion and Gemini.