What’s Up September 2023

A monthly look at astronomical events in the sky and on Earth

Compiled by Steve Sawyer

Hi welcome to September What’s Up.. I hope everyone has booked their tickets for York Astro’s 50th Anniversary on the 2nd, as the program of speakers is excellent!
So onto what’s happening this month, well dark skies return with the arrival of Autumn and the time around the equinox has proven to be an excellent time for Aurora spotting. There’s also a comet to look out for too.

Something else I found out about September is the Earth’s atmosphere tends to be more stable, resulting in better viewing conditions for telescopic observations. This stability minimizes the blurring effects caused by atmospheric turbulence, allowing for clearer and sharper views. There are several reasons for this. Cooling temperatures, reduced convective heating, a weaker jet stream, and settled weather patterns contribute to calmer and clearer air.

So what’s on this month?

Sky Diary

4thMoon near Jupiter
5thMoon near Pleiades
6thLast Quarter Moon
9thPeak of the e-Perseids
10thMoon near Caster and Pollux
11thMoon near Venus
12thMoon near Venus
13thMoon near Regulus
15thNew Moon
18thVenus at Max brightness
21stNeptune at oposition
22ndFirst Quarter Moon & Mercury Elogation
23rdAutumn Equinox
26thMoon near Saturn
29thFull Moon (last Supermoon of the year)

Sky Maps

Looking South on the 15th at 22:00

Looking North on the 15th at 22:00

Septembers Objects

The Sun

Not too many active sunspots at the time of writing but there are around 94 current active sunspots and 0 spotless days so far this year.

Whilst solar activity is independent of the the Earths tilt as we approach the time of the equinox the Earth’s magnetic field and the solar wind are aligned in a way that can increase the intensity of geomagnetic storms. This alignment allows solar wind particles to interact more effectively with Earth’s magnetosphere, resulting in a higher likelihood of auroras being observed. so as we move towards the autumn equinox activity may increase. So keep a look out for activity.


For more info on the sun and solar weather look here : –


And our own Met-office have an excellent space weather forecast page here Space Weather – Met Office

The Moon

The full moon this month takes place on the 29th and is the last supermoon of 2023. Septembers Moon is commonly know as the harvest moon.

Ai generated image of the harvest Moon, I think this would make a good Stephen King book cover!

The Harvest Moon occurs around the time of the autumnal equinox, which falls between September 21st and 23rd in the Northern Hemisphere. During this period, the angle between the ecliptic—the plane of Earth’s orbit around the Sun—and the horizon becomes shallow, causing the Moon to rise closer to the horizon.

Unlike other phases of the Moon, where its rise times vary each day, the Harvest Moon rises around the time of sunset for several consecutive nights. This unique characteristic results in a shorter time gap between sunset and moonrise. In some cases, the time difference can be as little as 20-30 minutes, as opposed to the usual 50 minutes or more.

The combination of the Harvest Moon’s shallow angle of ascent and its synchronized rise with sunset provides several evenings of bright moonlight. This extra illumination was historically beneficial to farmers during the autumn harvest, as they could work late into the evening with the aid of the Moon’s light.

The Harvest Moon’s proximity to the horizon during its rise can cause it to appear larger and more reddish or orange than usual. This reddish hue is a result of the Moon’s light passing through more of Earth’s atmosphere, which scatters shorter wavelengths of light and allows the longer wavelengths (such as red and orange) to dominate.

See the sky diary for this months lunar events as there are some nice viewing opportunities .

A full lunar calendar can be found here :-




Not visible at the start of the Month but from the 20th September, Mercury (mag –0.5) rises around 5 am, well to the lower left of Venus. It’s at maximum separation from the Sun on 22 September.


A Morning object Venus is one of the planetary highlights of the month. By the end of September, the planet is rising as 3 am, so early we see it against a truly dark sky, and at its maximum brightness (magnitude –4.5). There’s a pretty sight when the crescent Moon hangs nearby on the mornings of 11 and 12 September


Not visible this month


Visible in Aries from around midnight until morning.


Saturn lies in Aquarius and is above the horizon all night long and reaches it’s highest point in the sky this month. Saturn’s rings are currently facing with the northern edge tilted towards Earth


Also found in Aries and rises at around 9pm.


September is a good time to view this small blue planet. Neptune can be found in Pisces and is visible all night.

Meteor Showers


1st September is the peak of the Aurigrids but they’re active until the 5th. Somewhat spoilt by a 98% lit moon. The radiant is in Auriga which is high above the horizon.

e-Perseids (Epsilon Perseids)

Not to be confused with Augusts Perseids, as they come from a different comet. These peak is on the 9th September but can be seen from the 5th-21st, with the radiant being in Perseus. This is a weaker shower with around 5-10 meteors per hour during the peak.


So we have a new comet to look out for!
Discovered on August 11th by Japanese amateur astronomer Hideo Nishimura and now named after him comet C/2023 P1 (Nishimura) is currently in the constellation Cancer with a mag of 7.0 and is slowly getting brighter.

How to find it

September 5: C/2023 P1 (mag 5.5, elongation 27.7°) enters the constellation Leo.
September 6: C/2023 P1 (mag 5.2, elongation 26.3°) passes 0°6′ away from the star Ras Elased Australis (mag 2.95) in the constellation Leo.
September 9: C/2023 P1 (mag 4.2, elongation 21.2°) passes 0°33′ away from the star Adhafera (mag 3.4) in the constellation Leo.
September 12: C/2023 P1 (mag 3.3, elongation 15.5°) reaches its closest approach to the Earth at a distance of 0.85 AU and passes 1°38′ away from the star Zosma (mag 2.6) in the constellation Leo.
September 14: C/2023 P1 (mag 2.7, elongation 12.7°) passes 0°6′ away from the star Denebola (mag 2.1) in the constellation Leo.
September 15: C/2023 P1 (mag 2.5, elongation 12.1°) enters the constellation Virgo.
September 17: C/2023 P1 (mag 2.3, elongation 12.2°) reaches perihelion in the constellation Virgo.
September 21: C/2023 P1 (mag 3.2, elongation 14.0°) passes 1°23′ away from the star Porrima (mag 2.7) in the constellation Virgo.

These are the other viewable comets this month, the ones listed below start at mag 7 and go to mag 13.

C/2023 E1 (ATLAS)11
C/2020 V2 (ZTF)9
103P/Hartley 27
12P/Pons- Brooks11
C/2022 A2 (PanSTARRS)12
C/2022 W3 (Leonard)13
C/2019 T4 (ATLAS)13
C/2021 X1 (Maury- Attard)13

Deep Sky (DSO’s)

This month its the turn of Aquarius. Whilst not among the most striking constellations, Aquarius, also known as the Water Carrier, boasts an ancient lineage. Its origins trace back to antiquity, with the Babylonians linking this celestial region to water due to the Sun’s transit during the rainy season. In Greek depictions, Aquarius takes the form of a figure pouring from a Water Jar, represented by a central cluster of four faint stars. This action is portrayed as the liquid cascading downward onto Piscis Austrinus, the Southern Fish constellation.

NGC 7293 (Helix Nebula)

The Helix Nebula (NGC 7293) is a nearby and notable planetary nebula in the Aquarius constellation. Its intricate structure resembles a cosmic eye and represents the final stage of a star’s life. Located about 700 light-years away, the nebula showcases a central star that once resembled our Sun.


Messier 2 (M2) is a prominent globular star cluster in the Aquarius constellation. Located around 37,000 light-years from Earth, M2 showcases a collection of densely packed old stars spanning about 175 light-years in diameter. Its bright appearance and larger size make it an accessible target and unlike some clusters, M2’s stars are resolvable, allowing appreciation of the individual stars within its structure

NGC 7727

NGC 7727 is an irregular galaxy. Its classification as an irregular galaxy comes from its lack of defined spiral or elliptical structure, giving it a unique and unstructured appearance. Positioned at a considerable distance from Earth (83 million light years), NGC 7727 showcases an intricate and visually engaging arrangement of stars, gas, and dust.

NGC 7009 (Saturn Nebula)

This planetary nebula is known for its resemblance to the planet Saturn. It features a central star shrouded in a gaseous ring, resulting in a striking visual similarity to the ringed planet.

Messier 72 (M72)

Another globular cluster in Aquarius, M72 presents a more subdued appearance compared to M2. Its fainter stars and smaller apparent size make it a rewarding challenge

Double Stars

Aquarius offers a few intriguing double stars, such as Psi Aquarii and Epsilon Aquarii.

ISS and other orbiting bits

DateVisibleMax Height*Appears
Thu Aug 31, 3:49 AM3 min33°33° above SSE
Thu Aug 31, 5:21 AM7 min58°10° above WSW
Fri Sep 1, 3:02 AM1 min15°15° above ESE
Fri Sep 1, 4:35 AM5 min54°27° above WSW
Sat Sep 2, 3:48 AM3 min47°47° above SSE
Sat Sep 2, 5:21 AM7 min54°10° above W
Sun Sep 3, 3:02 AM1 min17°17° above E
Sun Sep 3, 4:35 AM5 min58°32° above WSW
Mon Sep 4, 3:48 AM3 min50°50° above SE
Mon Sep 4, 5:21 AM6 min41°12° above W
Tue Sep 5, 3:01 AM1 min16°16° above E
Tue Sep 5, 4:34 AM4 min49°35° above WSW
Wed Sep 6, 3:48 AM2 min37°37° above SE
Wed Sep 6, 5:21 AM5 min27°13° above W
Thu Sep 7, 3:02 AM< 1 min10°10° above ESE
Thu Sep 7, 4:35 AM3 min34°34° above SSW
Fri Sep 8, 3:48 AM1 min17°17° above SE
Fri Sep 8, 5:22 AM3 min16°14° above SW
Sat Sep 9, 4:36 AM1 min16°16° above S

Check the website listed for sightings after this date . Use the this NASA website for exact timings for York overpasses. York, England, United Kingdom | Sighting Opportunity | Spot The Station | NASA

Useful Resources







Top 10 Winter Sky Targets for Skywatchers | Space

and of course the sky at night magazine!

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