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.

Hopping Double Stars in Cassiopeia

February 26, 2020 by Brian Ventrudo Filed Under: Deep Sky

White arrows point to the objects in this brief tour of the constellation Cassiopeia. Created with SkyX by Software Bisque.

When time is tight and the weather turns cold, I turn to a class of celestial objects that are very forgiving of observing conditions, light pollution, and telescope aperture: double and multiple stars. There are thousands of these objects visible during the year. Many are run-of-the-mill sights. But many more present a lovely appearance in a small telescope, revealing color, brightness contrast, and a jewel-like appearance that appeal to the artistically inclined while also packing plenty of physics and sheer challenge to the observer.

In this instalment of Cosmic Pursuits, I share with you three double and multiple stars in and around the throne of the legendary Ethiopian queen (along with a couple of extraordinary ‘bonus objects’). So grab a small telescope and head out to see them for yourself. The map above shows you where to find these relatively bright star systems and ‘bonus objects’… [Read more…] about Hopping Double Stars in Cassiopeia

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Faint Fuzzies in and Around Pegasus and Andromeda

December 23, 2019 by Joe Bergeron Filed Under: Deep Sky

The globular cluster M15 in the constellation Pegasus.
Image credit: Joe Bergeron.

I write this in late October. Every night, the sky is four minutes more wintry than it was the night before. For now, the sky is still dominated by the constellations most associated with Autumn, even as the Summer Triangle slides past the meridian and the Pleiades rise in the east.

The constellations of northern autumn, Pegasus and Andromeda, linger well into the winter months and offer many deep sky wonders for observers equipped with a good telescope. One recent autumn evening, as the Pleiades rose in the east, I set about looking for a handful of these sights in my 8-inch Edge HD Schmidt-Cassegrain telescope [Read more…] about Faint Fuzzies in and Around Pegasus and Andromeda

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A Low-Power Romp in the Late-Summer Sky

September 13, 2019 by Joe Bergeron Filed Under: Deep Sky

Messier 24, the Small Sagittarius Star Cloud, at right. Image credit: Martin Heigen/Flickr.

Let’s follow last week’s sky tour with a pair of objects where low power is so essential that without it, you might miss them entirely. The first is the open cluster IC 4665, which lies a degree or two north of the star Beta Ophiuchi (Cebalrai). The cluster was “discovered” by astronomer after astronomer, but it didn’t make enough of an impression on anyone to stick around in the astronomical consciousness until it was finally added to the Index Catalog in 1908. In my little telescope at 18x I see a very scattered group of twenty or so easily seen stars spreading across a degree or more of sky. Try as I might, I could not imagine a compelling picture in this random assortment of star dots. Surrounding the most nearly crowded part of the cluster are a few more isolated pairs and individual stars that give the impression of being cluster members. This might be a better object for binoculars than for any telescope. [Read more…] about A Low-Power Romp in the Late-Summer Sky

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Deep Sky Tour: Nebulae in Cygnus

September 7, 2019 by Joe Bergeron Filed Under: Deep Sky

The North America Nebula (left) and the Pelican Nebula (right). Image credit: Terry Hancock via Flickr.

In my previous sky tour, I talked up the virtues of observing deep sky objects using fairly high magnifications with a reasonably big 8-inch f/10 telescope. This time around, let’s veer to the opposite extreme and take a tour of a series of celestial objects that are best seen using small telescopes, low magnifications, and wide fields of view.

Cygnus, the Swan, which is as emblematic of northern-hemisphere summer as any other constellation, holds two of the best examples of wide-field objects which are visible nearly overhead in late northern summer, and low over the northern horizon for southern-hemisphere observers [Read more…] about Deep Sky Tour: Nebulae in Cygnus

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High-Power Hercules

July 11, 2019 by Joe Bergeron Filed Under: Deep Sky

The globular cluster Messier 13 in the constellation Hercules. The far more distant galaxy NGC6207 is at lower left. Image credit: Roth Ritter.

When sight-seeing larger nebulae (like the North America Nebula) and big star clusters (like the Double Cluster or Beehive), it’s usually best to stick with lower magnification and wider fields of view to take in the entire object. But most deep sky objects benefit from greater magnification, sometimes much greater. To demonstrate this, I prowled around in the constellation of Hercules, using my 8-inch Celestron Edge HD scope and an 8mm eyepiece, giving a magnification of 250x.

The first object on my tour was the planetary nebula NGC 6210. Like many planetaries, it has a high surface brightness that enables it to bear high magnifications well. At low powers it looks like a tiny bluish dot. 250x brings out considerable visual character in this 16 arc second object. Slightly oval, its edges are diffuse. Colorful as many planetaries are, it shows an aqua tint with hints and flashes of a fierce electric blue. I found that an 8-inch scope isn’t quite big enough to show these colors strongly in this particular object, but a 12-inch or larger instrument will make them unmistakable, and then you’re viewing an exotic object indeed. I did not consistently see the nebula’s central star, though this should not be difficult at magnitude 12.7. This may be due to the consistently rough seeing I experience in this valley of the southern Sierra Nevada range, where I’m surrounded by mountains on all sides. This tends to muddle the faint star into the bright glow of the nebula.

[Read more…] about High-Power Hercules

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