Jupiter and Saturn are dead easy to find this year – you really can’t miss them, close together down in the southern part of the sky. But finding the other giant planets, Neptune and Uranus, is much more of a challenge. This page is all about finding Neptune, which is well-placed for observing from the later summer right until the end of the year.
You may think that just because you’ve got a Go To telescope, the problem is solved, but it’s not as easy as that. Neptune is actually quite faint, and even if your Go To goes to pretty well, the chances are that you’ll be presented with several stars that might be Neptune. So our guide shows you how to find Neptune even with binoculars or a small telescope, given a good sky and dark enough conditions. In late summer you’ll have to stay up after 10 pm, but during autumn it will be higher in the sky in the early evening.
Start out by finding the Square of Pegasus, using the diagram below. Mars makes this easy to find, and although the stars are not very bright (about the same as those in the Plough) they are easy to spot.
Next you need to find some much fainter star patterns — the Water Jar of Aquarius and the Circlet in Pisces. These are visible from average out-of-town or even outer suburbs skies with the naked eye, but if not you will need to use binoculars.
From those, you need to pinpoint the 4th magnitude star Phi Aquarii as shown on the map, below and between the Circlet and the Water Jar. Fix your binoculars on this star, then look to its left.
Neptune looks like a faint star to the left of Phi Aquarii. But there are several faint stars it could be, so use the map below to work out which one it is. Being a planet, it moves position, but not very much from night to night. The diagram shows its positions for every 10 days from the end of August, with dates shown every 20 days. As you can see, it slows down towards the end of the year.
The circle surrounding Phi is 5º across, which is the same as a typical pair of 10 x 50 binoculars. If you can pinpoint Phi, hopefully you’ll be able to see much fainter stars as well, plus Neptune, which is magnitude 7.8 in August and mag 7.5 in December.
If you want further help, here’s a video recorded live under the stars