1781–1800 of 1,934 results
Plato proves the point

Moon

The Mysteries of Plato

The crater Plato is one of the superstars for observers of the Moon. It's big, conspicuous with its dark floor ringed by a bright rim, and long a subject of speculation, and controversy.

The craters Messier and Messier A

Moon

Messier on the Moon

Oblique impact resolves the mystery of one of the most bizarre crater pairs on the Moon: Messier and Messier A. Previous explanations for this crater pair ranged from imaginative to fantastical. All were wrong.

Mare Nectaris

Moon

Rings and Things

Mare Nectaris is the smallest of the circular maria on the Moon; lavas extend only 350 kilometers from shore to shore. But the Nectaris basin is beautifully defined by the spectacular Altai Scarp, which forms the southwestern rim of the basin.

Hipparcos satellite

Celestial Objects to Observe

Mining Hipparcos's Buried Treasure

The satellite caught tantalizing pieces of light curves for many new variable stars. Now it's time to fill in the details.

Sun

Solar Filter Safety

Before an eclipse occurs the media often provides information on how to watch the event safely. Unfortunately, despite the best intentions, inaccurate or confusing information on safe observing techniques is often provided. Here are the facts.

Sun

Sketching Sunspots

Looking for a daytime astronomy project to pursue? Why not set your sights on our nearest star?

Celestial Objects to Observe

Nova Hunters

Few observers have spotted an ever-elusive "new" star. Fewer still have done it twice. Observing styles and techniques are as varied as the searchers themselves.

Celestial Objects to Observe

The Benson Prize

If saving the Earth from destruction isn't enough incentive to find near-Earth asteroids, there's a prize for the amateur who discovers one.

Binary star artwork

Celestial Objects to Observe

A Treasure-Trove of Variable Stars

Some of the Hipparcos satellite's unfinished business provides fair game for backyard observers.

Variable Stars

The Minima of Algol

Now you can calculate the dates and times (local and Universal Times) when the eclipsing variable star Algol should be at its dimmest (magnitude 3.4 instead of its usual 2.1).

The constellation Leo

Variable Stars

The Lure of Variable Stars

Studying and recording the ups and downs of variable stars is a pleasant pastime that can also be scientifically rewarding. Here's a simple project to get you going.

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

Planets

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.

Celestial Objects to Observe

A Chain of Galaxies Near M92

Many interesting but faint objects are often overlooked when they're beside a "showpiece" object. A collection of galaxies near M92 are a good example of this.

Deep Sky

A Galaxy-Hop in Leo

Even with a modest telescope and a poor sky, you can ferret out many faint, far galactic wonders by using a good map.

Celestial Objects to Observe

A Pair of Grand Galaxies

If you think all galaxies are faint, fuzzy blobs, think again. Here are two easily-seen galaxies that will change your mind.

NGC 2440

Deep Sky

A Collection of Bipolar Planetary Nebulae

Butterflies of the Milky Way await scrutiny with telescopes small and large.

The Helix Nebula

Celestial Objects to Observe

Hunting Down the Helix

Despite its dodgy reputation, this planetary nebula is easy to find (for both Northern and Southern Hemisphere observers) if you go about it the right way.

Orion Nebula

Deep Sky

A Pair of Nice Nebulae

When you leave the planets, moons, and comets of our solar system behind, you enter the realm of the deep sky, a place of subtle glows and faint lights.

Comin' our way Friday

Celestial Objects to Observe

Hunting Asteroids From Your Backyard

You can discover an asteroid tonight. Digital technology and the CCD revolution have given amateurs the ability to do it. Here's how.

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