Deep Sky Observing

Articles about how to understand, find, and see celestial objects including stars, galaxies, nebulae, and star clusters with binoculars, telescopes, and the naked eye.

A Little Cluster in the Big Dog

February 16, 2017 by Brian Ventrudo Filed Under: Deep Sky

NGC 2362, the Tau Canis Majoris cluster. Credit: Adam Block/Mount Lemmon SkyCenter, University of Arizona.

The constellation Canis Majoris, the ‘Big Dog’, is home to many fine open clusters of blue-white stars along the stubby Orion Arm of the Milky Way. There are some real gems here, including the modest but delightful open star cluster NGC 2362, a group that hosts some of the youngest-known stars. Centered on the bright star τ (tau) Canis Majoris, this cluster, in a telescope, looks like a large diamond set among many smaller blue-white gems [Read more…] about A Little Cluster in the Big Dog

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NGC 2477 – The Electric Guitar Cluster

February 10, 2017 by Brian Ventrudo Filed Under: Deep Sky

NGC 2477 (also known as Caldwell 71) is an open cluster in the constellation Puppis. It contains about 300 stars, and was discovered by Abbe Lacaille in 1751. The cluster's age has been estimated at about 700 million years. NGC 2477 is a stunning cluster, almost as extensive in the sky as the full moon. It has been called "one of the top open clusters in the sky", like a highly-resolved globular cluster without the dense center characteristic of globular clusters. Credit: J. Perez/ESO. — NGC 2477 (left) and NGC 2451 (right) are one of the most beautiful pairs of star clusters in the sky Credit: J. Perez/ESO.

We turn our gaze to the southern reaches of the constellation Puppis, south and east of the bright star Sirius and Canis Major, to examine two stunning star groups in a rich field of the Milky Way.

The first stop is the star cluster NGC 2477. Discovered by Nicolas de Lacaille (the ‘father of southern astronomy’) in 1752, this is a glorious star cluster, bright enough to be visible without optics from southern latitudes. It’s a fantastic binocular object, but it’s best viewed at low-power with a small telescope where it fits in the same field of view as an adjacent star cluster, NGC 2451. At a distance of 3,700 light years, NGC 2477 is one of the richest and densest of open star clusters and looks a little like the loose globular cluster M71 in the constellation Sagitta. The cluster has an impressive 1,900 members and spans about 37 light years. It’s also an ancient cluster, about 1 billion years old, and likely has lost many members since its birth to gravitational perturbations from other stars and star clusters [Read more…] about NGC 2477 – The Electric Guitar Cluster

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The Allure of Carbon Stars

January 27, 2017 by Brian Ventrudo Filed Under: Deep Sky

The carbon star R Leporis. Credit: Damian Peach

For visual observers with small optics, the colors of the deep sky range from subtle to nonexistent. Galaxies and nebulae cast too little light to stimulate the color-sensing cone cells in our retinas, so they appear pale gray-white or, in the case of a bright planetary nebulae, gray-green. Bright stars are a little more colorful. Betelgeuse appears clearly orange, even to the unaided eye, Rigel shines blue-white, and the showpiece double star Albireo in the constellation Cygnus shows off a blue-green primary and red-orange secondary in even the smallest telescope. Otherwise, star colors are quite subtle, especially to new stargazers. But there is one exception– carbon stars. These deep ruby-red stars, which dredge up nuclear soot from their innards, give off a striking glow that’s easy to see in a small telescope. See your first carbon star and you’ll want to see many more [Read more…] about The Allure of Carbon Stars

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The Attendants of Mirfak

January 19, 2017 by Brian Ventrudo Filed Under: Deep Sky

The star Mirfak and its 'Attendants', the cluster known as Melotte 20, are at the bottom of this image, just right of center. Closer to the center of the image, just rightward, lies the famous Double Cluster. — The star Mirfak and its ‘Attendants’, the cluster known as Melotte 20, are at the bottom of this image, just right of center. Closer to the center of the image, just rightward, lies the famous Double Cluster.

Nearly overhead in the after-dinner hours of a northern winter night, the rich constellation Perseus offers even a modestly-equipped amateur astronomer many hours of pleasant stargazing. Named after the great hero of Greek mythology, Perseus finds itself in the starry plane of the Milky Way Galaxy where thousands of brilliant blue-white stars have coalesced in the the last few tens of millions of years. Near the star Mirfak, or α (alpha) Persei, the brightest star in Perseus, lies a particularly dazzling collection of associated blue-white stars that make up a loose cluster often called the “Attendants of Mirfak”. This little group is a beautiful sight in binoculars [Read more…] about The Attendants of Mirfak

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Three Clusters and a Cheshire Cat

January 13, 2017 by Brian Ventrudo Filed Under: Deep Sky

The stars along the northern Milky Way rising in the eastern sky. To the right lies the Hyades above which is the smaller Pleiades star cluster. To the right lies the constellation Auriga, the Charioteer. — The stars along the northern Milky Way rising in the eastern sky. To the right lies the Hyades above which is the smaller Pleiades star cluster. To the left of center in this image lies the constellation Auriga, the Charioteer.

Visible nearly overhead in the northern hemisphere, the bright constellation Auriga makes for pleasant viewing this time of year. The constellation, which looks like a big hexagon about 15° across, sits in a fine star field along the northern Milky Way directly opposite the much richer sky near the galactic center in Sagittarius. Auriga also holds the dazzling star Capella, the most northerly first-magnitude star in the skies. The constellation is also visible above the northern horizon from most populated parts of the southern hemisphere. Whether you have a pair of binoculars or a small telescope, make an appointment to examine the three finest open star clusters of Auriga– M36, M37, and M38– along with a smiling asterism embedded in the stream of the Milky Way [Read more…] about Three Clusters and a Cheshire Cat

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