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.
September offers great views of Jupiter as it comes to opposition, and Saturn, which has just passed it. Neptune also reaches opposition this month but the views are not as impressive.
Mars looks so much better this month as it heads for its own opposition in December. Uranus will reach opposition in November and is visible all night long this month.
Mercury and Venus are both moving closer to the sun and are not visible this month.
All of the images below can be opened full screen in a new tab by clicking on them
Mercury
05th September
Mercury sets 40 minutes after the sun making it practically unobservable today.
15th September
The time gap has closed below half an hour so we still can’t see the small planet.
25th September
Mercury passed in front of the sun two days ago and is now a morning planet but it only rises 15 minutes before our star.
Mercury passes in front of the sun (inferior conjunction) on 23 September and so is practically impossible to observe this month.
Dedicated observers might just catch a glimpse of it after sunset in the first few days of the month, or before sunrise at month’s end. To do that, you’ll need to know exactly where you’re looking and have a clear view of the horizon. Even so, your views will be fleeting before the planet sets or the sun rises.
Venus
05th September
Just after 6am and the bright planet is only 4° over the horizon. It doesn’t change much all month.
15th September
At 6:30, the sun is less than half an hour from rising and Venus is 4° high in the east.
25th September
Now it’s 7am and we can’t practically see venus because the sun is minutes from breaking the horizon.
Like Mercury, Venus closes in on the sun this month and disappears from our view. It doesn’t pass behind our star until 23 October but, even though that’s a month away, we won’t be able to observe the brightest planet from about the middle of September because the sky is too bright; Venus rises only minutes before the sun.
If you do catch sight of it at the start of September, you’ll observe that it is completely illuminated – its disc is full, and that’s because it is soon passing behind the sun and is reflecting sunlight back to us from all of the surface we can see. However, it is about as far away from us as it gets, so its disc is smaller than ten arcseconds across now.
Mars
05th September
At 5am Mars is high above the southeastern horizon. Its disc is ten arcseconds wide.
15th September
64° over the horizon, we’ll find Mars in the constellation of Taurus this morning before dawn breaks.
25th September
Still 5am and fractionally higher at 67°. The Red Planet shines at magnitude -0.5 this morning and is unmistakable.
After looking at two planets disappearing from view, it makes a pleasant change to be looking at one that’s coming to the fore once more. It’s been almost two years since Mars was as large and bright as it is now, and we’ve still got a way to go until it reaches its peak.
By the end of September, we should be spotting the more obvious surface features, even in an average scope, as its disc broadens to 12 arcseconds wide. With the widening profile comes a brightening surface, and the Red Planet shines at magnitude -0.6 by the month’s end, making it the fifth brightest object in the northern hemisphere night sky after the moon, Venus, Jupiter and the star Sirius.
Although Mars is highest in the sky around dawn, it is rising before 11pm at the end of September, when it can be seen low in the east.
Jupiter
05th September
At midnight, the giant form of Jupiter is one-third of the way above the horizon towards the zenith in Pisces.
15th September
Eleven days before its closest approach since 1969, we can see Jupiter 40° high before midnight, shining at magnitude -2.9.
25th September
Opposition is tomorrow. Right now, the Jovian disc is almost 49 arcseconds wide and shines brighter than all except Venus and the moon.
It has felt like a long time coming, but Jupiter’s closest approach to Earth since 1969 is upon us!
At its peak, the massive planet will be almost 50 arcseconds wide and shine at magnitude -2.9. As with all oppositions, the planet will be visible all night long, rising at 7pm and setting 12 hours later. It is highest in the sky a little after 1am.
For all your viewing needs, there is a full guide to observing the planet included with the Virtual Astronomy Club. Click this link for all the details of what to look for this month while the planet is bright, large, and visible all night.
Saturn
05th September
Opposition for Saturn is behind us but we still have great viewing. This is the scene at 11pm when Saturn is 33° high in the south.
15th September
At 11pm, the ringed planet is in Capricornus shining at magnitude 0.4, it is 18 arcseconds wide.
25th September
This view at 10:30 shows good evening viewing of the planet in the south.
Last month’s opposition was brilliant and although the peak might be behind us, we still have excellent viewing of the ringed planet.
The disc width and brightness barely change over the course of September and peak viewing, when the planet crosses the southern horizon, is before 11pm by the end of the month.
Uranus & Neptune
15th September – Uranus
This view at 5am shows Uranus 68° above the southern horizon, although the bright moon won’t help viewing this month.
15th September – Neptune
This view shows the sky at 11pm when Neptune is near Jupiter about 37° over the southeast horizon.
Both of the two most distant planets offer good viewing this month, they are both rising in the evening and setting in the morning. The best time to see Uranus is 4am and for Neptune is 1am.
Neptune reaches opposition on 16 September but the disc will still be only 2.4 arcseconds wide.
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.