21–40 of 49 results

History and Sky Lore

Observing Earth from the Moon

Ever wondered what it would be like to see the Earth from the Moon? Join Bob King as he explores this from the perspective of the Apollo 17 astronauts.

Eight planets await

Explore the Night with Bob King

See All Eight Planets in One Night

Four planets are great, but how about eight? You can see them all in a single night in the next couple weeks — if you play your cards right.

Celestial Objects to Observe

Observe Changes on Mars

The nearby Red Planet displays remarkable changes every apparition. Whenever Mars approaches opposition, keep an eye out for some of these differences.


Find Jupiter's Moons - Interactive Observing Tool

Use our interactive observing tool to say which of the planet's four largest moons is which.


Transit Times of Jupiter's Great Red Spot

Calculate when the Great Red Spot will cross Jupiter's central meridian — that's the best time to see the famous storm through your telescope.

Celestial Objects to Observe

Find Saturn's Moons: Interactive Observing Tool and App

With help from our interactive JavaScript utility, you can always tell which of Saturn's brightest moons is which.


The Elusive Moons of Uranus

Take the observing challenge: Find as many as five of the brightest moons of Uranus in a large backyard telescope using our interactive observing tool.


Track Triton, Neptune's Largest Moon

Triton, Neptune's largest moon, is a tricky find. Our Triton Tracker observing tool can help users of moderate to large telescopes spot this distant moon.

Astronomical Tools

Mars Profiler: Which Side Is Visible?

To compare what you see on Mars with a map, you need to know which side of the planet you're looking at. Our handy Mars Profiler tells you that and more, for any date and time.

Brothers in Blue

Explore the Night with Bob King

Uranus: In Seventh Heaven with Planet Seven

With our eyes often glued to the bright classical planets, Uranus is easy to overlook. Now well-placed for viewing at a convenient hour, why not pay this pale blue dot a visit the next clear night?

Open All Night

Explore the Night with Bob King

Saturn's Splendid Summer Show

It's showtime for the King of the Rings! Time to get your telescope out to see and share Saturn, which comes to opposition this week.

Paired Together for Another Week

Explore the Night with Bob King

It's Not Over Till The Fast Planet Sinks

This week and early next will be your last chance to see five planets — six if you count Earth — at dawn.

Why is Jupiter's Great Red Spot shrinking?


Jupiter's Not-So-Great Red Spot

Astronomers don't know why Jupiter's iconic Great Red Spot has been gradually shrinking since the 1800s — or why the downsizing has accelerated during the past two years. Update: On May 15th, NASA released newly taken images of the Great Red Spot (at bottom below) to show its declining size…

Jupiter and GRS

Celestial News & Events

How to See Jupiter: Big, Bright, and Beautiful

Jupiter, the King of Planets, is a captivating sight no matter how you look at it.

Saturn and its rings

Celestial Objects to Observe

Viewing Saturn: The Planet, Rings and Moons

Viewing Saturn is an old favorite for every telescope user. Here's a guide to seeing all that you can see on the ringed planet.


A Saturn Almanac

Spectacular Saturn is a perennial favorite of telescope users everywhere. Click here to find printable data on the positions of Saturn's rings and planets.


Mercury, Messenger, and Observers

As the first images are released from Messenger's flyby of the innermost planet, previous ground-based observations are proving to be surprisingly accurate.


Catching the Messenger of the Gods

Mercury is a rewarding challenge for planetary astrophotographers, as this amazing image by Massachusetts amateur John Boudreau demonstrates.

Celestial Objects to Observe

Phenomena of Jupiter's Moons

Virtually any telescope will show Jupiter's four Galilean satellites and their interesting interactions with the planet or its shadow.

Sketch of Jupiter


Jupiter: The Ultimate Observing Guide

Viewing the solar system¹s largest planet can be more than fun — even with a modest telescope, you can make observations of lasting scientific value.