In this month's Sky Notes:

• Planetary Skylights
• September Meteors
• Lunar Eclipse, Venus and Pleiades lunar Occultation
• Autumnal Equinox
• September Night Sky
• September 2025 Sky Charts

Planetary Skylights: 

Saturn and Neptune both come to opposition. Jupiter almost makes it into the evening sky but is a fine post-midnight object. Venus continues to dominate the dawn sky - even though it is quite low. Mercury soon departs the dawn sky. Uranus is located below the Pleiades.

 

Saturn is first of the naked-eye planets to rise, visible low in the east shortly after 20:45hrs at the start of September and before 19:15hrs by the month's end. Saturn reaches opposition on September 21st visible from sunset to sunrise, culminating 32 degrees above the south horizon around 00:30hrs BST from our latitude. This is still 3 degrees below the celestial equator, which it crosses in 2026.  Located between the tail of Cetus and the faint loop of stars marking the western fish in Pisces, Saturn gradually edges back in retrograde motion toward the Pisces/Aquarius border which it crosses on the last day of September.  At magnitude +0.62 the creamy white hue of Saturn will appear conspicuous amongst the fainter, neighbouring stellar backdrop and has little discernible scintillation (twinkling).

Saturn can present an impressive view through the eyepiece; however, observers should be aware that the ring system’s inclination is currently less than 2.5 degrees, narrowing further to 1.5 degrees by October. As a result, only limited detail will be visible, primarily with larger telescopes, and mainly at the extremities of the rings. By November, the rings will appear nearly edge-on again. Nonetheless, a quality 100mm (4") instrument can still demonstrate just how narrow the rings have become.   

Observers may be able to identify several of Saturn's many moons; eight are accessible to amateur telescopes. Rhea, Tethys, Dione, and Iapetus are most frequently observed with instruments exceeding 200mm (8") in aperture. Titan, by far the largest of Saturn’s moons, is consistently visible in smaller telescopes as a bright point of light, completing its orbit around Saturn approximately every 16 days. Around the date of opposition, there will be an observation window exceeding five hours during which Saturn remains above 20 degrees altitude under favourable seeing conditions. Additionally, the full Moon will appear above Saturn on September 8th.  

 

Neptune reaches opposition this month, occurring two days after Saturn does and is situated just under two-degrees upper left of Saturn. With a magnitude of +7.8, Neptune is observable with binoculars, although a telescope is necessary to discern its small blue-grey disk, which measures 2.8 arc-seconds in diameter. An instrument with a 100mm (4") aperture is generally adequate for this but telescopes exceeding 150mm (6") will reveal it more clearly. On September 8th, Neptune will be positioned between Saturn and the full Moon.

 

Jupiter is the next planet to rise in the early morning hours (01:30hrs) at the start of September and only makes the late evening sky by a few minutes at the end of the month. Residing just below the stars of Gemini, Jupiter is very conspicuous reaching magnitude -2.12 and climbing to 45+ degrees in elevation, well above poor seeing air by the month's end.  

Jupiter remains an impressive object even when observed through small telescopes, with its oblate shape—measuring nearly 40 arc-seconds across—clearly visible in the eyepiece. Observers can identify the planet's darker atmospheric bands, the Great Red Spot (when present), and the Galilean moons positioned near its disk; these moons complete their orbits within days to weeks, while Jupiter itself rotates in under ten hours. The arrangement of the Galilean moons shifts nightly, providing varied observational opportunities. Larger instruments offer enhanced views of Jupiter’s cloud features, making the Great Red Spot and moon shadow transits more prominent. Notable and accessible GRS and shadow transit events for observers will be highlighted in the coming months.   

 

 

Uranus is located in Taurus, approximately five degrees below the Pleiades star cluster, situated roughly midway between the A1/A2 Tau pair and 13 & 14 Tau. With a magnitude of +5.8, Uranus is technically visible to the naked eye under very dark skies. Through binoculars, it appears as a faint point, telescopes with apertures of at least 80mm (3+ inches) are necessary to resolve its small 3.7 arcsecond greenish disk, which becomes more distinct with instruments of 150mm or larger.

 

Venus, commonly referred to as the 'morning star', is visible in the eastern dawn sky. At the beginning of September, it can be observed from 04:00 hours, with visibility shifting to an hour later toward month's end. Despite its pronounced brightness at magnitude -4.0, Venus offers limited morning visibility for observers at mid-northern latitudes, typically lasting just over two hours. The planet remains close to the horizon, reaching a maximum elevation of approximately 20 degrees before daylight obscures the view.  

Venus has a close encounter with Regulus - chief star in Leo across a 4-day period from the 18th - 22nd.  Regulus almost sits upon the ecliptic and is visited by planets and Moon regularly. On this occasion Venus passes just to the north of Regulus. On the 19th a waning crescent Moon joins the party. 

 

Mercury rapidly drops below the east horizon in first week of September following its most favourable dawn apparition of the year. On the first few mornings of September, you can spot Mercury some distance lower left of Venus a few degrees above the ENE horizon. At magnitude -1.2 Mercury will appear quite bright. View approximately 40 minutes before sunrise.

 

 September Meteors, 

There are no major noteworthy meteor showers in September; however, you may spot a few Piscids which have two peaks: the 8th and the 21st.  Rates are low, with only 6 or 7 per hour at best, barely more than sporadic levels.  As with all meteor showers early morning viewing will be best. Moonlight will interfere for the first date. 

The Perseid meteor shower was mostly hidden from the public gaze, Moonlight severely hindering, washing out the majority of examples. Those brighter Perseids spotted were done so in the early morning hours but were captured by some amateur astronomers. Mark captured nothing on camera, and spotted just one visually when imaging the Venus - Jupiter conjunction on Aug 13th at 04:20hrs. Not a great haul then.
       

Lunar Eclipse 

A Total Lunar Eclipse will occur on September 7th; however, observers in the UK will only be able to view the conclusion of totality, as the Moon will be positioned just a few degrees above the east-southeast horizon during its rise into the early evening sky.  

The beginning and middle phases of the eclipse take place while the Full Moon remains below the horizon on September 7th. Depending on your specific location within the UK, the Moon will rise in the east-southeast at approximately 19:42hrs BST, with lunar totality concluding by 19:54hrs BST.  

As skies grow dark and the Moon pulls away from the ESE horizon, the umbral shadow should become obvious finally leaving the Moon around 20:55hrs BST.  The less conspicuous penumbral shadow (difficult to detect) does not leave the Moon until 21:56hrs BST. 

Due to the Moon's relatively low position in the sky during the more prominent phases of the eclipse, an unobstructed view toward the east-southeast is advisable. At this low elevation, the Moon typically exhibits an orange tint, making it noteworthy to observe any changes in hue during the eclipse event.  

 

Lunar - Pleiades Occultataion. 

The Moon will participate in another observable astronomical phenomenon as it passes in front of the Pleiades star cluster in an occultation on September 12th. The Moon will rise shortly before 21:00hrs, accompanied by the Pleiades already in the firing line. Over the following three hours, the Moon will transit directly through the open cluster, completely obscuring it from view. By midnight, the Pleiades will reappear as the occultation concludes.  

 

Venus - Moon Occultation.

Finally, the Moon occults Venus on September 19th - but in daylight for UK observers. The event will be challenging as both Venus, and the very slim waning crescent Moon will just be # degrees to the right of the Sun. Caution must therefore be exercised in endeavouring to observe the occultation. 

A GOTO telescope setup will be ideal enabling the observer to target either Venus (if set), or the slender Moon crescent. Venus will be located next to the faintly lit slither by 12:44hrs, so give yourself 10mins to track it down before this. Then watch over the next few minutes as the Moon slides in front of Venus, doing so around 12:48hrs. These times will vary wherever the observer is in the UK.

The occultation lasts just over an hour with Venus reappearing from the unlit side of the Moon around 14:06hrs BST. 

The occultation lasts just over an hour with Venus reappearing from the unlit side of the Moon around 14:06hrs BST. Trying to locate the Moon without a GOTO scope will be more problematic, not to mention potentially dangerous. The chart below may be of help, when at 11:15hrs the Moon and Venus will be due south just under 50 degrees in elevation. Observers would have to continually follow the Moon and Venus until the occultation itself. It will be interesting to see how visible it will be. Good luck and be wary of the Sun.

 

The Autumnal Equinox

Meteorological autumn commences on Sept 1st in the northern hemisphere, whereas astronomical autumn does not officially commence until Sept 22nd this year, the date of the autumnal equinox. Either way Autumn is rapidly approaching as the evenings draw in. 

On the date of the autumnal equinox, from our perspective the Sun re-crosses the celestial equator and retreats southwards, arcing ever lower above the south horizon.  At an equinox the Earth's poles are neither inclined toward, or away from the Sun, but are parallel to it. Hours of daylight and darkness will be almost equal across the globe. The northern hemisphere will continue to tilt away from the Sun with evenings becoming darker earlier, until the Sun eventually reaches the lowest position on the ecliptic - the winter solstice - around December 21st.

 

September Night Sky

When conditions are conducive September is one of the best months for amateur astronomers to explore the night sky.  By mid-month evenings are rapidly drawing in, with the majority of stars visible by 21:00hrs BST (Whitby - North Yorks) and most deep sky objects accessible by 22:15hrs.  Should temperatures remain on the mild side, it can therefore be a pleasure to be observing.  For UK observers September is also the month to fully appreciate the magical aspect of the Milky Way, at its most conspicuous to the naked eye from dark locations.   

As dusk falls five stars are first to emerge; Arcturus, in the west, the “summer trio” of Vega, Deneb and Altair – located overhead and midway up in the south, together with Capella low to the North. The pieces in the celestial constellation jigsaw puzzle then gradually fall into place over the next hour as the fainter stars emerge by 22:15hrs. Look to the west to locate brilliant amber hue of Arcturus in constellation of Boötes.  

Upper left of the Herdsman, note the appealing starry circlet of Corona Borealis - the Northern Crown, Alphecca or Gemma its lead star and centre stone of the tiara. Any star of equal magnitude visible below and left is exciting news, the recurrent nova star TCor B! 

Much of the WSW aspect is defined by two large, fainter, ill-defined groups. The figure of Hercules sprawls across the higher regions of the west a little above Corona.  It is best identified by the ‘keystone’ asterism. Below Hercules the larger and fainter outline of Ophiuchus extends down towards the SW horizon.  

High in the WNW, the familiar outline of the Plough, part of Ursa Major, the Great Bear is well placed.  Follow the natural curve of the handle to locate Arcturus and Boötes, then utilise the ‘pointer’ stars in the bowl of the Plough to locate the pole star - Polaris, due north.  Polaris marks the tail tip of the Little Bear - Ursa Minor.  The brilliant star seen twinkling low above the NNE horizon is Capella in the circumpolar winter constellation of Auriga. The zenith (directly overhead) is occupied by the head of Draco, the body of which winds between the two bears.

Due South, Sagittarius - the Archer straddles the horizon (see in focus – The Archer part 1).  If skies are transparent look for the large asterism referred to as the ‘Teapot’, the outline of which resembles a more ‘angular’ type of pot slightly tilted as if pouring a cuppa!  If you have a pair of binoculars or low powered telescope, spend some time exploring the magnificent star clouds and various nebulae located within Sagittarius.  

The summer ecliptic runs not far above the south horizon and along with Sagittarius much of the S - SE aspect is occupied by zodiacal constellations.  Following the Archer are the stars of Capricornus - the Sea Goat.  The aquatic theme continues low in the ESE with Aquarius - the Water Bearer and Pisces - the Fish, its inconspicuous stars meander down to and then back up from the east horizon.  The planet Saturn currently resides close to the Pisces – Aquarius border. 

High overhead to the South, extending down to the SSE, the constellations of the ‘summer triangle’; Lyra, Cygnus and Aquila dominate.  A short distance above Altair in Aquila, note the small arrow shaped group of Sagitta together with the close-knit group of Delphinus situated to its left.  Delphinus is one pattern that with a little imagination does resemble the outline of a dolphin leaping out of water.  It is also bizarrely known as ‘Jobs coffin’.  

Climbing up from the NNE horizon the great hero Perseus stands proud, whilst the distinctive “W” pattern of Queen Cassiopeia, sits on her throne above his shoulder. 

The eastern aspect of the sky is dominated by just a few constellations, particularly the winged horse Pegasus, which stands 2-3 hand-spans above the horizon. It is best identified by “the great square”, four stars arranged thus and enclosing an area of sky seemingly devoid of naked eye stars. Between Pegasus and Perseus, the chained princess Andromeda, daughter of Cassiopeia, stretches. Situated within the borders of Andromeda, our “sister” galaxy can be glimpsed with the naked eye on clear moonless nights later in the month. 

To locate the Andromeda galaxy, star hop along a well-spaced chain of stars extending eastwards away from the upper left-hand star (Alpheratz) of the Square of Pegasus, marking the main body of Andromeda. Two stars along this chain at a star called Mirach, turn northwards, passing a further two fainter stars. Lying next to the second of these you should notice an elongated wispy patch of light, the Andromeda galaxy, a spiral system like our own. It is easily seen with binoculars, however if the sky is sufficiently dark and transparent, it is visible to the naked eye, making it the most remote object detectable without optical aid, a staggering 2.6 million light years distant. If you are not sure use the “averted vision” technique, i.e. - don’t look directly at it, but slightly to one side.

Below Andromeda sit two small constellations, Triangulum, below which lie the crooked line of stars marking Aries - the Ram.  Along with the Andromeda galaxy and the Milky Way, the third spiral galaxy in our local group is in Triangulum -M33 (the other pinwheel galaxy in the sky), seen as a misty patch in binoculars or rich field telescopes.  

Finally, charging over the horizon in the ENE is Taurus the Bull, led by the exquisite open cluster of the Pleiades or Seven Sisters marking the bull's tail.  The sight of the Pleiades reminds that winter waits in the wings, but for the time being Autumn is set to take centre stage! 

By late September the summer Milky Way is well placed for observation and this year moonlight will be absent. Find a dark location and allow 15 minutes for your eyes to adapt to the conditions. The Milky Way should be noticeable as a ghostly river of light dissecting the sky in a NE to SSW direction. Follow this milky stream from where it rises in the NNE through the constellation of Auriga, sweeping up through Perseus and into the ‘W’ pattern of Cassiopeia. A humble pair of binoculars will be useful in exploring these constellations containing numerous star fields pleasing to the eye. 

Moving through Cepheus, the Milky Way then crosses overhead directly through the long axis of Cygnus, the Swan (sometimes called the Northern Cross) highlighted by Deneb a member of the summer triangle asterism marking the tail of the Swan. Here the Milky Way divides into two channels which flow either side of a 'darker, elongated island' midstream. Known as the ‘northern rift’ it is an intervening dust cloud approximately 4 thousand lights distant which partly obscures the stellar multitude beyond.

Cascading down through Aquila, passing bright Altair, the most southerly member of the summer triangle, the Milky Way broadens before flowing into Sagittarius - straddling the SW horizon. In this direction nebulae and star clusters abound, rich pickings to keep the optical observer more than satisfied if skies are transparent. The galactic centre lies amidst the celebrated star clouds of Sagittarius, some 27000 light years away.

Revered by ancient civilizations as a divine water course or spiritual path, the true nature of the Milky Way has been understood for over a century.  However, within the last few decades data obtained from across the electromagnetic spectrum from varied sources has reshaped our understanding of the galaxy.  It would appear the Milky Way galaxy is not the classic multi-armed spiral with a central hub structure once thought; (like a Catherine wheel on bonfire night).  Our galaxy is a barred spiral galaxy over 120,000 light years in diameter with just two major arms and several lesser ones.

The central bar consists of stars orbiting in highly elliptical paths and is approximately 28,000 light years in length, bulging at the centre.  At the very centre lurks a massive black hole of some 4 million solar masses.  Our Sun is located on the edge of a quiet stellar neighbourhood midway between two major arms known as the Orion spur, some 26,000 light years from the galactic centre. The arms themselves are approximately 1,500 light years thick, the nearest sections of which lie some 6,500 light years away.

Our stellar citadel is truly vast with latest data analysis estimating it contains between 150 and 350 billion other suns and several trillion planets.  And yet, all that accounts for just 6 percent of our galaxy's mass, the rest taking the form of dark matter!  

September then, offers a fantastic opportunity to step outside one fine and clear evening to appreciate the majesty of our galactic heritage. Make that time and take a leisurely and awe-inspiring cruise down the Milky Way river. 

 

     September Sky Charts. 

Looking North Sept 15th - 21:00hrs BST	Looking East Sept 15th - 21:00hrs BST
Looking South Sept 15th - 21:00hrs BST	Looking West Sept 15th - 21:00hrs BST
Northern Aspect Sept 15th - 21:00hrs BST	Southern Aspect Sept 15th - 21:00hrs BST
Northern Aspect (dawn) Sept 15th - 05:00hrs BST	Southern Aspect (dawn) Sept 15th - 05:00hrs BST