2141–2160 of 2,250 results

Variable Stars

R and T Coronae Borealis: Two Stellar Opposites

One is usually bright but fades unexpectedly; one is almost always faint but brightens unexpectedly. Check them out with binoculars.

Sun through hydrogen-alpha filter


Observing the Sun Safely: Sunspots, Faculae, and Flares

The surface of the Sun is a dynamic, living place that can change unpredictably from day to day.

Full Moon

Celestial Objects to Observe

Observing the Full Moon

The full Moon is very bright, but there are still many fascinating features to observe during this or any phase when you look far from the terminator.

Celestial Objects to Observe

Nebulae of the Deep South

On a long-awaited tour of the southern Milky Way, Alan Whitman discovers many splendid sights in far-southern skies.

Celestial Objects to Observe

How and Why to Make Occultation Timings

Lunar and planetary occultations may be appreciated for their intrinsic beauty, but in order to contribute scientifically valid data you need to apply certain techniques.

Celestial Objects to Observe

Seeking Summer's Dark Nebulae

Amateur skygazers can spend hours roaming ghostly clouds of interstellar dust. You just need to know where to look.

Aurora borealis over Iceland

Celestial Objects to Observe

An Aurora Watcher's Guide

Want to see an aurora? In this introduction to auroral phenomena, an expert explains what to look for, when, and how.

Comet Hale Bopp


Secrets of High-Power Comet Observing

Although large, bright comets are infrequent visitors to our skies, faint comets appear on a regular basis. Here are some observing hints that will make your comet-watching more enjoyable.

urban observer

Deep Sky

Observing Secrets of Deep-Sky Objects Revealed

Here's how to hone your galaxy-hunting skills — and what to expect at the eyepiece.

Comet Sherrod

On the Road with David Levy

How to Report a Comet Discovery

So you think you’ve found a comet? Here are some steps to follow in verifying your find.

Celestial Objects to Observe

How to Estimate a Comet's Brightness

Comets are notorious for not following predictions, but even judging the magnitude of a bright comet that's right in front of you is not straightforward.

Celestial News & Events

Mercury in the Morning

Amateurs are observing this elusive planet more successfully than ever before; try spotting it yourself.

Crescent Moon and Venus at sunset


Seeking Thin Crescent Moons

Here are some tips for hunting one of nature's most captivating sights.

Celestial News & Events

Asteroid Flyby Caught!

On July 3, 2006, an 800-meter (half-mile) asteroid called 2004 XP14 flew past Earth at a distance a little greater than that of the Moon.

Comet Halley

Celestial Objects to Observe

Eta Aquariids: Halley's Comet Crumbs

Flecks of dust shed long ago by Edmond Halley’s famous namesake arrive like clockwork each year, creating a minor meteor shower in early May.

Celestial News & Events

The April 1st Pleiades Occultation

The waxing crescent Moon made quite a spectacle crossing the Pleiades on April Fool's Day 2006.

Deep Sky

RS Ophiuchi Finally Blows its Stack

This famous recurrent nova has just erupted for the first time in 21 years, reaching magnitude 4.8 on February 13th.

Quadrantid meteor


History of the Quadrantid Meteors

Read about the history and source of the Quadrantid meteor stream, which provides one of the most intense annual meteor displays. Its brief, sharp maximum lasts only a few hours in early January.

Celestial News & Events

A Mars Record for the Ages

On August 27, 2003, at 9:51 Universal Time, the centers of Earth and Mars will be only 34,646,418 miles apart. Has Mars ever been this close before?

A bullseye basin, volcanic domes and lava-flooded crater highlight Friday morning's crescent Moon


A Rare Glimpse of Mare Orientale

On five consecutive mornings beginning January 29th, early morning risers have an opportunity to glimpse the Moon’s most spectacular "hidden" landform.