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The Casual Observer
September continues the season of Djilba. This is a time of wet weather but a slow change into warmer days. Fittingly, the Spring Equinox is on September 23, marking the beginning of astronomical spring. From here on out, it should get warmer as the days get have increasing amounts of daylight.
The Milky Way still stretches across the sky and makes for good viewing in the evenings. The Southern Birds group, made up of the constellations Pavo, Phoenix, Grus and Tucana makes for excellent viewing in the southeastern sky all month.
Credit: Stellarium
There is a total lunar eclipse – a ‘Blood Moon’ this month, though it’s not for the early sleepers. Beginning at 11:30pm on September 7, the Moon will be fully in Earth’s shadow by 1:30am on September 8 and will be the distinctive dark red colour that gives these eclipses their name. What’s happening is that faint sunlight scattered through Earth’s atmosphere is still able to reach the Moon, even though it is behind the Earth. Due to the way light scatters through Earth’s atmosphere, only the red light makes it all the way to the Moon, resulting in the stunning colour change. The Moon will have completely passed through earth’s shadow by 4:30am on September 8 and the eclipse is over.
Credit: Public Domain
Correspondingly, there is a sister partial solar eclipse two weeks later on September 22 over the South Pacific Ocean, New Zealand and parts of Antarctica. We won’t be able to see this from Perth.
Saturn is at opposition on September 21. This means it is exactly opposite the Sun in the sky. If you point one hand at the Sun and the other hand toward Saturn, you will be pointing in exactly opposite directions. The observational consequence of this is that Saturn rises as the Sun sets and will be up all night. This is the best time of year to see the ringed planet in all its glory as it also means we will see the planet face on.
Credit: Stellarium
ISS sightings from Perth
The International Space Station passes overhead multiple times a day. Most of these passes are too faint to see but a couple of notable sightings* are:
| Date, time | Appears | Max Height | Disappears | Magnitude | Duration |
| 1 Sep 6:46 PM | 10° above SW | 86° | 10° above NE | -3.8 | 6.5 min |
| 15 Sep 05:39 AM | 10° above WNW | 57° | 10° above SE | -3.6 | 6.5 min |
Table: Times and dates to spot the ISS from Perth
Source: Heavens above, Spot the Station
*Note: These predictions are only accurate a few days in advance. Check the sources linked for more precise predictions on the day of your observations.
Moon phases
Full Moon: September 8
Last Quarter: September 14
New Moon: September 22
First Quarter: September 30
Dates of interest
September 7: Total Lunar Eclipse begins late evening and continues into morning of September 8
September 14: 10th anniversary of first detection of gravitational waves
September 14: Mars close to Spica
September 21: Saturn at opposition
September 23: Spring equinox
September 24: Moon next to Mars
Planets to look for
Venus and Jupiter still dominate the eastern morning sky. Jupiter moves higher to the northeast, while Venus gets lower in the sky, sinking into the morning twilight by the end of the month. They are joined by the Moon on September 18 for a nice viewing.
Credit: Stellarium
Saturn makes for excellent viewing all month as its location at opposition makes this the best time of year to see it.
Mars hangs in the west during the evenings on its interminable march across the sky. It’s quite faint now at about magnitude 1.6. It has a close encounter with the brighter star Spica on September 14, passing about 2 degrees from it.
Credit: Stellarium
Mercury is lost in the glare of the Sun this month and is a useless piece of sh*t at the best of times anyway.
Constellation of the month
Scutum the Shield
Scutum is a tiny constellation – the fifth smallest of them all – located just north of Sagittarius, placing it almost directly overhead during September evenings. Astronomer Johannes Hevelius orginally named it Scutum Sobiescianum after Polish King John III Sobieski (‘The Sheild of Sobieski’) but these days we just remember the first part of it.
Credit: Stellarium.
Scutum is unusual in that it straddles part of the Milky Way but is still quite faint, with the brightest star in its boundaries Alpha Scuti being a miniscule magnitude 3.8. Despite this, in fact, because it straddles the Milky Way, it presents no shortage of astronomical wonders.
Scutum contains the fascinating but sadly uninspiringly named planetary nebula IC 1295. Despite their name, planetary nebula have nothing to do with planets. Rather, when a Sun-like star dies of old age it throws off its outer layers of gas, exposing its hot core. The radiation from the hot core of the now dead star ionises the expelled gas, causing it to glow in all sorts of pretty colours, which gives us the beautiful images in our telescopes that we call planetary nebulae. The name comes from the days of ye olde – planetary nebulae tend to look round in shape through a telescope, just like planets – so early astronomers named them thus. We now know they have nothing to do with planets.
Credit: ESO
Scutum is also home to the star UY Scuti. This star is one of the largest known stars in the galaxy, an appalling 900 times wider than the Sun, at minimum. Coming in at 125,000 times brighter than the Sun, its surface would probably extend past Jupiter if we placed it in our Solar System.
You should really watch this video.
Objects for the small telescope
Saturn – The jewel of the Solar System
The ringed planet is a must see this month. Rising in the early evening as the Sun sets, it is visible to the naked eye as a yellowish blob. A small telescope quickly reveals the rings and the noticeable flattening of Saturn at its poles as the planet’s rapid rotation squashes it out. You might also see a couple of its myriad moons. The latter half of the month is the best time for viewing, as Earth’s pesky Moon will be out of the way.
Credit: Stellarium
