Where is Neptune tonight?

Why you can’t see Neptune with the naked eye

Neptune is the faintest of the eight planets. NASA’s fact sheet puts it at magnitude 7.7 around opposition, and never brighter than 7.67. On the magnitude scale, higher numbers mean fainter objects. In John Bortle’s dark-sky scale, published by Sky & Telescope, only an excellent dark-sky site lets the eye reach stars of magnitude 7.6 to 8.0, and even then it takes trained eyes and effort. For practical purposes, Neptune is a binocular and telescope target only. The British Astronomical Association (BAA) puts it at about magnitude 7.8 and says binoculars are the minimum.

That makes Neptune different from every other planet on this site. You won’t stumble across it; you have to set out to find it.

What binoculars and a small telescope show

In binoculars, Neptune looks like one more faint star among many. The way to find it is with a detailed finder chart from an astronomy app, magazine or almanac, centered on the constellation listed in the table above. Start from the nearest bright star, step from one star pattern to the next until you reach the right field, and match what you see to the chart.

Because it looks exactly like a star, confirmation comes from movement. Sketch the field or take a phone photo through the eyepiece, then look again a few nights later. The point that has shifted against the others is Neptune.

A telescope adds a little more. According to the BAA, a small telescope shows Neptune as a tiny dot that doesn’t quite look like a star, and a 6-inch (150 mm) instrument shows a clear small disk with a pale hint of color. NASA’s fact sheet gives an apparent size of only 2.2 to 2.4 arcseconds, smaller than Uranus and a small fraction of Jupiter’s width. Neptune’s large moon Triton is easily recorded with cameras, the BAA notes, but no surface features of the planet are visible in backyard telescopes.

Why its visibility comes and goes

Neptune takes about 165 years to orbit the Sun, according to NASA’s fact sheet, so it creeps along the zodiac and stays in the same constellation for many years. Earth laps it a little more than once a year: the synodic period is 367.49 days, so each opposition comes about two days later than the previous one.

At opposition, Neptune is opposite the Sun in our sky. It rises around sunset, sets around sunrise and is highest near midnight, giving the longest observing window of the year. Its brightness barely changes over the year because it is so far away; what changes is how long it stays above the horizon in darkness. In the months after opposition, it sets earlier each evening until it is lost behind the Sun at conjunction, then returns in the morning sky.

Tips for seeing Neptune

• Choose a dark, moonless night. Moonlight and light pollution hide faint stars of Neptune’s brightness, even in binoculars. Our dark-sky places page lists certified sites by state.
• Steady the binoculars. A tripod adapter or resting your elbows on a car roof makes faint points much easier to see.
• Look near opposition. The weeks around opposition, listed above, give the most hours with Neptune high in a dark sky.
• Find Uranus first. If you’re new to faint-planet hunting, Uranus is the easier target and good practice for star-hopping.

Our guide to finding planets explains star-hopping and how to tell planets from stars, and the planets page shows which planets are visible tonight.