The Planets
Planet Data For September
Click on any planet below to go straight to its section.
The table below shows key data for the planets this month, including rise, transit and set times, as well as magnitude, apparent size and position data (right ascension and declination).
Events that occur when the sun is below the horizon are shown with a black background and white text. All other events happen when the sun is in the sky and other for not visible for observation.
The month of September lets us see all of the planets, even the most distant ice worlds of Uranus and Neptune, although Venus presents an evening challenge.
Mercury delivers some of its best views of the year in the first half of the month, with Mars and Jupiter also looking bright in the predawn sky. It’s Saturn that wins the prize of ‘best planet’ this month because it reaches opposition on the 21st.
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Mercury
05th September
Half an hour before sunrise and Mercury is almost 10° over the eastern horizon with its seven-arcsecond disc.
15th September
It’s not so high now but this is one of the last best chances of the year to observe this illusive planet.
25th September
As always, Mercury quickly moves to be too close to our sun for us to see it.
This is one of the best Mercury displays of the year. For the first half of September, Mercury is far enough away from the sun, and the line of the ecliptic is steep enough to push it relatively high above the horizon before sunrise.
It is farthest from the sun on the fourth of the month, but we get good views for a week either side of that date. Your telescope reveals a disc about six arcseconds across, but that is only about one-third lit.
As September wears on, the Mercurial disc once again dives towards the sun and we lose the chance to see it once more.
Venus
05th September
Although Venus is a decent distance from the sun, the ecliptic is shallow and so Venus is very low.
15th September
At 8pm, the brightest planet is a few degrees over the western horizon.
25th September
The picture is little improved as we head towards the end of the month. This is the scene at 8pm.
Venus has been a tricky customer to spy for many weeks and the situation shows little sign of changing this month. Although our brightest planet is moving away from the sun, the ecliptic (the line the planets appear to travel along) is so shallow that Venus barely scrapes over the horizon after sunset.
The picture will steadily keep improving, but it’ll be November before we’re getting decent views of the planet.
Mars
05th September
At five am, the Red Planet is roughly midway between the horizon and overhead in the east.
15th September
The Martian disc is now the same size as Mercury’s, at seven arcseconds across.
25th September
This is the view at 5am again, but we’ll soon be able to see the planet before midnight.
Mars is at its highest before dawn breaks. As it moves closer to us, so its disc grows, reaching 7.5 arcseconds by the end of the month and shining brightly at magnitude 0.5.
In October, we’ll be able to start observing the Red Planet in the evenings but, for now, we’ll need to content ourselves with an early morning alarm clock to get the best that it has to offer.
Jupiter
05th September
Jupiter remains close to Mars in September, but pulling away. This is the view at 5am.
15th September
Also at 5am, Jupiter is now 60° high in the southeast and between the ‘horns’ of Taurus the bull.
25th September
Orion underpins the forty-arcsecond disc of Jupiter this morning, shining at magnitude -2.5.
Jupiter’s disc continues to grow and brighten as we head towards its opposition at the start of December. By the end of September, it’ll be a huge forty arcseconds wide and shining at magnitude -2.5, making the third brightest night sky object after the moon and Venus.
Whenever you choose to look at it in September, you’ll get a great view, so long as you’re avoiding the brightest of the moon. When you do point your telescope its way, don’t forget to pull in the views of nearby Mars as well.
Saturn
05th September
With opposition three weeks away, we can see Saturn in the evening. This is the view at 11pm.
15th September
At the same time ten days later, Saturn is accompanied by the moon 37° high in the southeast.
25th September
Four days past opposition and at 10:30 in the evening, Saturn is about 40° above the southeast horizon.
It’s opposition month for Saturn, which means that, on the 21st, it will be directly opposite the sun with us in the middle. This is the time of year when we’re closest to the planet and so it’s at its largest and brightest. However, Saturn is so far away that it doesn’t change all that much whenever we look at it. The best thing is that we can now see it in the evening and it’s visible all night long.
A glimpse with your telescope reveals that the rings are getting closer and closer to being edge-on to our line of sight, so they’re much less pronounced than you might expect. The disc of the planet is about half the size of Jupiter’s, at 19 arcseconds, and shines at magnitude 0.7.
Why not try to spy some of its moons while you’re looking at it?
Uranus & Neptune
15th September – Uranus
At five in the morning, Uranus is up close to the zenith in the south and not too far away from the Pleiades, can you spy it?
15th September – Neptune
At the same time, Neptune has passed its highest point of the night but is still observable 28° over the southwest horizon.
Both of the frozen giants at the edge of the solar system are visible this month. Like so many of their closer siblings, they too are best seen in the early hours of the morning. If you’re already up looking for Mars and Jupiter, why not give both of these distant icy worlds a try?
All Planets Viewer
Use the table below to see when each of the planets is observable for each day this month. Click on it for full screen.
A planet is classed as observable when it is more than 10° above the horizon and the sky is dark enough for it to be observed.
Planet ephemeris tables produced with the kind permission of Dominic Ford. Sky images are courtesy of SkySafari Pro 6.