| Date | Event | Time |
|---|---|---|
| 2 | Aurigid Meteor Shower (ZHR = 6) | 04:00 a.m. |
| 5 | Close approach of Jupiter and Moon | |
| 10 | September ϵ-Perseid Meteor Shower (ZHR = 5) | 04:00 a.m. |
| 12 | Moon at Apogee (Distance = 406,247.170 km) | 11:43 p.m. |
| 17 | Comet Nishimura at perihelion | |
| 22 | Mercury at Greatest Elongation West | 09:16 p.m. |
| 23 | September Equinox | 02:50 p.m. |
| 28 | Moon at Perigee (Distance = 360,007.215 km) | 08:59 a.m. |
|
Last Quarter | |
| Sep 07 | 06:21 AM | |
|
New Moon | |
| Sep 15 | 09:40 AM | |
|
First Quarter | |
| Sep 23 | 03:32 AM | |
|
Full Moon | |
| Sep 29 | 05:57 PM | |
| Date | Mercury | Venus | Mars | Jupiter | Saturn | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| Rise | Set | Rise | Set | Rise | Set | Rise | Set | Rise | Set | |
| Sept 01 | 06:25 am | 06:28 pm | 03:55 am | 04:19 pm | 07:26 am | 07:29 pm | 09:50 pm | 10:29 am* | 05:49 pm | 05:31 am* |
| Sept 11 | 05:11 am | 05:24 pm | 03:19 am | 03:46 pm | 07:13 am | 07:10 pm | 09:10 pm | 09:49 am* | 05:07 pm | 04:49 am* |
| Sept 21 | 04:34 am | 04:56 pm | 02:56 am | 03:25 pm | 07:01 am | 06:52 pm | 08:29 pm | 09:08 am* | 04:26 pm | 04:06 am* |
| Sept 30 | 04:46 am | 05:02 pm | 02:45 am | 03:12 pm | 06:50 am | 06:37 pm | 07:52 pm | 08:30 am* | 03:49 pm | 03:29 am* |
* = following day
 Figure 1: The view of the night sky featuring the prominent September constellations including its artwork at 09:00 p.m. on 15 September 2023 using the Stellarium software |
This September, Cygnus the Swan will be the northernmost constellation. Locating Cygnus in the night sky will be a breeze using its largest asterism, the Northern Cross. The Northern Cross is composed of the stars Albireo (Beta Cygni), Fawaris (Delta Cygni), Deneb (Alpha Cygni), Sadr (Gamma Cygni), and Aljanah (Epsilon Cygni) [2] (Figure 2a). Cygnus also contains two Messier objects, the open clusters Messier 29 and Messier 39. Other significant deep sky objects in the constellation include Cygnus X-1, a well-known X-ray source; the Fireworks Galaxy (NGC 6946), a spiral galaxy close to Cepheus; and the Blinking Planetary Nebula (NGC 6826) [2] (Figure 2b).
 (a) Constellation Cygnus and the asterism Northern Cross including its boundary |
 (b) Some interesting Deep Sky Objects in the artwork of Cygnus “The Flying Swan” |
| Figure 2: The formation of the Northern Cross and some prominent deep sky objects in the constellation Cygnus on 15 September at 09:00 p.m. using the Stellarium software | |
Vulpecula, the fox constellation, is a small, obscure constellation and can be observed lying within the Summer Triangle (Figure 3a). It is the location of the first planetary nebula ever found, the renowned Dumbbell Nebula (M27). The nebula’s double-lobed shape appears only in a telescope[2]. Lying below Cygnus is the constellation Delphinus. Although it is one of the smaller, fainter constellations, its characteristic diamond shape makes it simple to spot. This constellation does not house any deep-sky object; however, it has an asterism known as Job’s Coffin, formed by the brightest stars of Delphinus (Figure 3a). Another minor constellation in the northern sky is Equuleus, located between Aquila and Pegasus, which symbolizes the tiny horse or foal [2] (Figure 3a). Situated south of the celestial equator is the constellation Capricornus. Its name means the goat in Latin (Figure 3b). The constellation is a sea-goat, along with Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Sagittarius, Aquarius, and Pisces, Capricornus is a member of the zodiac family of stars [2]. Microscopium, a constellation located between Piscis Austrinus and Sagittarius is the home of two spiral galaxies, NGC 6925 and NGC 6923 (Figure 3b). It is challenging to observe because it is small and elusive. It represents the microscope and is unrelated to any myths. Its brightest star is named Gamma Micoscopii. Further down below south of the equator is the Indus (Figure 3b). However, there are no prominent stars in it. The constellation represents the Indian, referring to a native of either Asia or the Americas at the time the constellation was created [2].
 (a) Constellations Vulpecula, Delphinus and Equuleus visible in the northern sky including the position of M27 represented by the red circle |
|
 (b) Constellation Capricornus, Microscopium, and Indus visible in the southern sky |
|
| Figure 3: Some of the constellations best observed in September together with their corresponding artworks, constellation lines, and their boundaries using Stellarium Software. | |
 Figure 4: The view of the eastern sky on 23 September 2023 at 05:00 a.m., showing the position of Mercury, more than 1 hour after the exact event of dichotomy at 03:26 a.m, using the Stellarium application. |
Meanwhile, Mars is not visible the entire month due to its proximity to the Sun [3]. Venus, on the other hand, will be visible throughout the month, rising as an early morning object in the east before disappearing from view before daybreak [3]. On 18 September at 08:09 p.m., Venus will be at its greatest brightness in the constellation Cancer and will be shining at magnitude -4.5 however, Venus will not be visible at the horizon until 03:02 a.m. on 19 September [6]. Figure 5 shows the position of Venus before the exact time of the event since the planet can only be seen in the early morning in the eastern sky before sunrise.
 Figure 5: The view of the eastern sky on 18 September 2023 at 05:00 a.m., showing the position of Venus before the exact event of greatest brightness at 08:09 p.m., using the Stellarium application. |
Meanwhile, Jupiter and Saturn will be visible in the late evening sky on the eastern horizon [3]. On 05 September at 01:37 a.m., the waning gibbous Moon and Jupiter will make a close approach, passing within 3°04’ of each other [7] (Figure 6). After two hours, at 03:47 a.m. the pair will be in conjunction with the Moon, where Jupiter will be separated 3°18’ to the south of the Moon [8,9]. This close pairing is placed among the background stars of the constellation Aries and can be observed in the east northeastern horizon as soon as it rises at around 09:35 p.m. of 04 September.
 Figure 6: The view of the eastern sky on 05 September 2023 at 01:37 a.m. showing the close approach of waning gibbous Moon and Jupiter using the Stellarium application. |
The Waxing Gibbous Moon and Saturn will also be in conjunction on 27 September at 09:29 a.m., where Saturn and the Moon will be separated by 2°38’ [10]. Subsequently, at approximately 11:12 a.m., they will have a close approach, passing within 2°25’ of one another [11]. However, it will be unobservable due to its actual occurrence is during the day. Nevertheless, it will be best seen at around 07:00 p.m. in the east southeastern sky at the constellation Aquarius (Figure 7).
 Figure 7: The view of the east southeastern sky on 27 September 2023 at 07:00 p.m. showing the close approach of waxing gibbous Moon and Saturn, less than 8 hours, after the exact event at 11:12 a.m. using the Stellarium application. |
 Figure 8: The view of the northeastern sky during the peak of Aurigid on 02 September 2023 at 04:00 a.m. when the shower’s radiant is represented by the green solid circle. |
The September ϵ-Perseids is a meteor shower active from 05 September to 21 September. The September ϵ-Perseids is expected to produce 5 meteors per hour during its peak. The radiant of the shower, the constellation Perseus, rises in the eastern sky at around 09:03 p.m. and then will remain active until dawn breaks at around 05:20 a.m. The shower is likely to produce its best displays at around 04:00 a.m. on 10 September. The shower will peak close to the new moon, and so moonlight will present minimal interference. Figure 9 shows the position of the radiant in the eastern sky at 04:00 a.m. on 10 September [13].
 Figure 9: The view of the northeastern sky during the peak of ϵ-Perseids on 10 September 2023 at 04:00 a.m. when the shower’s radiant is represented by the green solid circle. |
No special tools, such as binoculars or telescopes, are needed to view meteor showers; they can be observed without them. To maximize the viewing experience, choose a dark location away from city lights and make sure that the sky is clear and moonless sky conditions [12, 13].
The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) and the National Astronomical Research Institute of Thailand (NARIT) are pleased to host this year's 13th Southeast Asia Astronomy Network Meeting (SEAAN 2023), which will be held in Manila, the Philippines, from 28 - 29 November 2023. The theme of the meeting is "Radio Astronomy Development in Southeast Asia."
The call for abstract and registration is now open.
Visit the official event link for more details: indico.narit.or.th/event/SEAAN2023
 Radio Astronomy Development in Southeast Asia (click image for full details) |
Notes:
*following day
• All times displayed are in Philippine Standard Time (PhST)
References:
[1] PAGASA Special Publication No. 840: The Philippine Star Atlas, 2019
[2] C. Guide, “Constellations: A Guide to the Night Sky, September Constellation” https://www.constellation-guide.com/constellations-by-month/september-constellations, Last accessed 2023-08-15, 2023
[3] D. Ford, In-The-Sky.org Guide to the night sky: “Objects in your sky: Planets” https://in-the-sky.org/data/planets.php?day=15&month=9&year=2023, Last accessed on 2023-08-15, 2023.
[4] D. Ford, “In-The-Sky.org Guide to the night sky: “Mercury at greatest elongation west” https://in-the-sky.org/news.php?id=20230922_11_101, Last accessed on 2023-08-15, 2023
[5] D. Ford, “In-The-Sky.org Guide to the night sky:Mercury at dichotomy” https://in-the-sky.org/news.php?id=20230922_11_102, Last accessed on 2023-08-15, 2023
[6] D. Ford, “In-The-Sky.org: Objects in your sky: ”Venus at greatest brightness” https://in-the-sky.org/news.php?id=20230918_11_100, Last accessed on 2023-08-15, 2023
[7] D. Ford, “In-The-Sky.org Guide to the night sky: “Close approach of the Moon and Jupiter” https://in-the-sky.org/news.php?id=20230904_15_100, Last accessed on 2023-08-15, 2023.
[8] The United States Naval Observatory. Multiyear Interactive Computer Almanac (MICA), Last accessed 2023-06-23, 2023
[9] D. Ford, “In-The-Sky.org Guide to the night sky: “Conjunction of the Moon and Jupiter” https://in-the-sky.org/news.php?id=20230904_20_100, Last accessed on 2023-08-15, 2023.
[10] D. Ford, “In-The-Sky.org Guide to the night sky: “Conjunction of the Moon and Saturn” https://in-the-sky.org/news.php?id=20230927_20_100, Last accessed on 2023-08-15, 2023.
[11] D. Ford, “In-The-Sky.org Guide to the night sky: “Close approach of the Moon and Saturn” https://in-the-sky.org/news.php?id=20230927_15_100, Last accessed on 2023-08-15, 2023.
[12] D. Ford, “In-The-Sky.org Guide to the night sky: “Aurigid meteor shower 2023” https://in-the-sky.org/news.php?id=20230901_10_100, Last accessed on 2023-08-15, 2023.
[13] D. Ford, “In-The-Sky.org Guide to the night sky: “September ϵ-Perseid meteor shower 2023” https://in-the-sky.org/news.php?id=20230909_10_100, Last accessed on 2023-08-15, 2023.
[14] Philippine Astronomical Handbook [15] D. Ford, “In-The-Sky.org Guide to the night sky: ”September equinox” https://in-the-sky.org/news.php?id=20230923_07_100, Last accessed on 2023-08-15, 2023.
[16] Minor Planet Center, ”MPEC 2023-P87 : COMET C/2023 P1 (Nishimura)” https://www.minorplanetcenter.net/mpec/K23/K23P87.html, Last accessed on 2023-08-24, 2023.
[17] NASA, JPL, ”C/2023 P1 (Nishimura)” https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?des=2023%20P1 Last accessed on 2023-08-28, 2023.
[18] Star Walk, ”New Comet Alert: C/2023 P1 (Nishimura) - A Naked-Eye Spectacle for September 2023” https://starwalk.space/en/news/new-comet-c2023-p1 Last accessed on 2023-08-24, 2023.
For more information, call or email:
Ms. Ma. Rosario C. Ramos, RCE
Chief, SSAS - RDTD
PAGASA - DOST
Diliman, Quezon City
Trunkline: 8284-0800 loc 3015, 3016, 3017
Email add: astronomy@pagasa.dost.gov.ph