Live observing guide
Neptune is too faint for the naked eye. Finding it is a navigation challenge that requires a telescope and an accurate chart.
BEYOND TONIGHT'S VIEW
Know this planet
- A year
- 59,800 days
- One orbit around the Sun · Earth days
- One rotation
- 16.1 hours
- Relative to the stars, not sunrise to sunrise
- Diameter
- 49,528 km
- Measured across the equator
- Mass
- 1.02 × 1026 kg
- Total mass of the planet
- Mean temperature
- -200 °C
- At 1 bar in the atmosphere; no solid surface
- Known moons
- 16
- Confirmed natural satellites
- Distance from Sun
- 4,515 million km
- Average distance along its orbit
- Gravity
- 11 m/s²
- Effective gravity at the 1-bar equator
- Mean density
- 1,638 kg/m³
- Mass divided by volume
- Ring system
- Yes
- Faint rings may need a spacecraft to reveal them
Rounded values. Moon counts checked on ; new discoveries can change the totals.
Experienced star-hopping and the satisfaction of finding a remote world
- A very faint blue point
- A tiny non-stellar disc at high power
- Slow movement against the surrounding star field
Observing tips
What you can really see
Neptune is not a naked-eye target. Expect a faint point in binoculars and a very small disc at the telescope.
Do not identify it by a vivid blue colour; images can make its colour and detail much more conspicuous.
Before you leave
- Use a precise chart of the surrounding faint stars, not just the direction on the horizon.
- Set the telescope on a steady mount and give it time to adjust to the outdoor temperature.
How to observe
- Find the correct star field at low magnification.
- Match the surrounding pattern and the plotted position before calling the point Neptune.
- Record its position and revisit on another night to check its movement against the stars.