Observe the sky: September 2025

There are those who see September as the new January—a month that marks the beginning of a new academic year, school term, or simply a time to return to routine after the holidays. For many of us, it’s a moment to set new intentions: adding workouts to our daily schedule, eating real food, planning better, adopting a new study method, and so on. And of course, “Observa el cielo desde Ciencias” won’t be left behind. We promise changes and more interaction in our Telegram group, so don’t hesitate to join us. Here’s the link! Without further delay, let’s begin!

September started with a waxing Moon that was dangerously approaching Earth’s shadow, which it met on the night of the 7th. Unfortunately, much of the country was cloudy, and this lunar eclipse went largely unnoticed. But September brings much more to our astronomical calendar. On one hand, we have Saturn and Neptune in opposition, marking an ideal time to observe both planets. On the other, we welcome the arrival of Autumn, as September 22 marks what we know as the Autumn Equinox.

On this special date, the Sun will be at 0° declination, meaning it will be on the celestial equator, crossing from the celestial Northern Hemisphere to the Southern. On this day, both hemispheres will receive the same amount of sunlight (not accounting for cloud cover). The equinoxes—spring and autumn—are the only two days of the year when this is true. On September 22, night will fall at the North Pole (the Sun will dip below the horizon), beginning a “night” that will last six months, until the Sun rises again at the Spring Equinox. Naturally, this day marks the beginning of Autumn for those in the Northern Hemisphere, but that’s not the case everywhere. In the Southern Hemisphere, this day marks the start of Spring.

Additionally, September 22 (along with the Spring Equinox) is the only day when the Sun will rise exactly in the East and set exactly in the West—and it will do so at every point on the planet, including the poles. Although equinox means “equal night (and day),” this isn’t quite true on the day of the equinox. On September 22, in Granada, Spain, the day will last 12 hours and 7 minutes. It will be on September 25 when day and night will be exactly 12 hours long (with the Sun above the horizon for 12 hours), known as the equilux.

Day	Time	Event
7	20:09	Full Moon
8	19:42	Moon in conjunction with Saturn, 3.50° N of Saturn
10	14:51	Moon at perigee ( 364680 km)
13	12:39	Mercury at superior conjunction
14	12:36	Moon in its last Quarter
16	14:21	Moon in conjunction with Jupiter, 4.49° N of Jupiter
19	14:23	Moon in conjunction with Venus, 0.74° N of Venus
21	07:19	Saturn at opposition
21	21:55	New Moon
22	13:38	Moon in conjunction with Mercury, 2.56° S of Mercury
22	20:18	Autumnal Equinox
23	14:39	Neptune at opposition
24	13:59	Moon in conjunction with Mars, 3.60° S of Mars
26	11:23	Moon at apogee ( 405549 km)
30	01:55	Moon in its first Quarter

Table 1: Main astronomical events of the month of September. Local time.

During September, the Sun not only crosses from the celestial Northern Hemisphere to the Southern, but it also drops a staggering 12° in declination in just 30 days. The shorter days are definitely becoming noticeable! For the Moon, however, September will be a fairly typical month. Aside from the eclipse on the 7th, it will begin the month in its waning phase and end with a first quarter Moon on the 30th.

Sun during September 2025. — **Figure 1:** Variation of the Sun's position during the month of September. Left: Maximum daily elevation of the Sun during the month. Right: Position in the sky if observed every day at the same time (12.00 UT). In orange the positions of the Sun throughout September; in yellow, throughout the year (analemma).

Moon during September 2025. — **Figure 2:** Observability and illumination of the Moon during the month of September 2025. In red the time zone (universal time, UT; local time = UT + 2) during which you will be able to observe the Moon. The vertical white lines indicate the time of the Moon's passage through the local meridian.

Moon during September 2025 (II). — **Figure 3:** Phases and Moon orbit during September 2025.

The most memorable planets to observe are, without a doubt, Venus (for its brightness), Saturn (for its rings), and Jupiter (for its equatorial bands and moons). Well, this month we’ll be able to enjoy Saturn, as it will be in opposition on the 21st. That said, it won’t be a particularly remarkable opposition. Saturn’s rings, although they always maintain the same tilt relative to the ecliptic, don’t appear that way from our point of view. In fact, in 2025 (specifically in March), Earth passed through the plane of Saturn’s rings, making them nearly imperceptible in September. Jupiter, the other gas giant, can only be observed during the second half of the night, so we’ll have to wait until October or November to include it in our observation activities. However, for those astronomy enthusiasts who own a telescope, here is a table where you can check all the events involving Jupiter’s moons throughout the month of September (tabla Jupiter).

Planets observability towards the beginning of September 2025 — **Figure 4:** Observability of the different planets of the Solar System from Granada in September 2025. In red, the time zone (universal time) during which you will be able to observe the different planets. The vertical white lines indicate the time of the passage of the various planets through the local meridian.

Planets observability towards the middle of September 2025 — **Figure 4:** Observability of the different planets of the Solar System from Granada in September 2025. In red, the time zone (universal time) during which you will be able to observe the different planets. The vertical white lines indicate the time of the passage of the various planets through the local meridian.

Planetary situation for the month of September 2025 in Granada. — **Figure 5:** Representation of the sky that will be observable at the end, beginning and middle of a typical September night from Granada (September 14th is chosen as representative). The positions of the planets as well as their motion relative to the fixed stellar background are indicated. For the planets with less apparent motion (Jupiter, Saturn, Uranus and Neptune) a zoom is included for tracking with telescopes.

The September sky still holds the majesty of the summer sky, dominated by the region of the galactic center in the direction of Sagittarius. However, fainter constellations like Pegasus, Andromeda, and Pisces are beginning to take on a more prominent role in the September sky. Objects such as the Andromeda Galaxy (M31), visible from dark skies with small telescopes, or M74 in Pisces (both galaxies), are typical targets of the sky in the season we’re entering this month.

The sky over Granada during the month of September 2025. — **Figure 6:** Representation of the sky that will be observable on a typical September night from Granada. The ecliptic is indicated (dashed line) as well as the main deep sky objects.

As always, the International Space Station also has its place in “Observa el cielo desde Ciencias.” In the following link, you’ll find a table (ISS table with the main visible ISS passes over Granada during this September. This month, we highlight the passes on September 10, 26, 28, and 29 (with magnitudes close to -3.5), all observable at very convenient times (just after sunset). For more details, check the table in the link.

And so we reach the end of September—a month of new beginnings and intentions that, who knows, might change our lives for the better. Once again, we thank you for the trust you’ve placed in us, and we warmly welcome the new students joining our activities or our University this year. Welcome!

Finally, remember that we’re open to suggestions on our Telegram channel, where you can also stay up to date with our activities and receive timely alerts about easily observable astronomical events and much more. Here’s the link! We hope to see you soon at our events. Wishing you a great start to the academic year—see you in Ciencias!

Clear skies!