Deep-sky objects: Small telescope and binocular targets

Deep-sky objects: A colorful oval cloud in space, blue in the middle to orange and red on the outskirts.
Amateur astronomers like to target deep-sky objects with their telescopes. The Ring Nebula, M57, in the constellation Lyra, is one such target. The white dot in the center of this nebula is a white dwarf. This planetary nebula came from a star that was once like the sun. Image via The Hubble Heritage Team (AURA/ STScI/ NASA).

What are deep-sky objects?

Deep-sky objects lie beyond our solar system and make great observing targets for those using optical aid under dark skies. Amateur stargazers sometimes refer to them as faint fuzzies. Unlike the nearby planets (which look like little disks through a telescope) or stars (which always look like pinpoints), deep-sky objects are hazy spots in the sky that start to take shape when viewed through binoculars or a telescope. Deep-sky objects generally fall into three categories: nebulae, galaxies and star clusters, including open clusters and globular clusters.

Some of the best deep-sky targets are those in the Messier catalog. Charles Messier was a comet hunter who methodically searched the skies for comets. He cataloged all objects that were not comets, but might be confused with them because they looked fuzzy.

He didn’t know it at the time, but he was creating a list of the best and brightest deep-sky objects. These groupings of stars, clouds of gas and dust in our Milky Way, plus galaxies beyond our own, are some of the most fun objects to track down with a telescope. So today’s amateur astronomers attempt to join a Messier Club, by observing all 110 Messier objects (or some subset of them). Or they perform Messier marathons, seeing as many of these objects as they can in one night.

A swirly, pink and blue figure 8 shaped cloud in a star field.
View at EarthSky Community Photos. | Scott MacNeill at Frosty Drew Observatory in Charlestown, Rhode Island, created this image of the Orion Nebula. It’s a composite he made from images taken on November 17, 2020. Thank you, Scott! The Orion Nebula, or M42, is visible even without optical aid as a hazy patch on the sword hanging from Orion’s belt.

Nebulae: Clouds of gas and dust

There are a few different types of nebulae, or clouds of gas and dust, that you can observe. There are emission nebulae, which include planetary nebulae, that glow because a star late in its life has puffed off a glowing shell of ionized gas. Then there are reflection nebulae, which are clouds of dust that aren’t glowing themselves but reflecting the light of nearby stars. Lastly are the dark nebulae, which are so dense that they block out the light from any background sources. Nebulae are usually found along the plane of the Milky Way where most of the stars in our galaxy reside.

Galaxies: Island universes

Not surprisingly, the best place to look for galaxies in the night sky is away from the direction of our own galaxy, the Milky Way. The Milky Way blocks the view of more distant island universes. The closest large spiral to Earth is also the easiest to spot: M31, or the Andromeda Galaxy. M81 and M82 are handy galactic targets for the Northern Hemisphere, because they’re visible year round.

White dots freckle a black background with a large blue and white swirl - the Andromeda galaxy - in the center.
View at EarthSky Community Photos. | Stunning capture of the Andromeda galaxy by Peter Forister. He caught the galaxy early in the morning on July 14, 2021. He wrote: “This was my first opportunity to photograph the Andromeda galaxy in 2021! I set up my equipment at 3:30 a.m. on my front porch in Charlottesville, Virginia.” Thank you, Peter! The Andromeda Galaxy, or M31, is also visible without optical aid as a hazy oval from dark country skies.
Small elongated glowing yellow smudge and similar oval smudge in darkness of space among scattered stars.
M81, or Bode’s Galaxy, right, is a nearly face-on spiral galaxy. M82, left, has the nickname the Cigar Galaxy. Image via Ken Christison. Thanks, Ken! These two galaxies are easy to spot with a small telescope in the constellation Ursa Major.

Star clusters: Open clusters

Open star clusters are young, loosely bound gatherings of stars. One of the most famous open clusters is the Pleiades, found in the constellation Taurus. Because this cluster is so close and large, you can view it best with binoculars or even the unaided eye. A telescope gives you too narrow a view and cuts out members of the cluster. The Beehive is another popular open cluster. The view of this deep-sky object improves with magnification.

Cluster of bluish stars with bright Venus below.
View larger at EarthSky Community Photos. | Kevin Saragozza captured this striking view of Venus and the Pleiades from Siracusa Plemmeiro on April 1, 2020. He wrote: “I positioned myself outside in my garden, not having the possibility to catch the alignment together with interesting terrestrial elements because of the Covid-19 quarantine. I preferred a view of the sky, the Pleiades and Venus, aligned in a vertical position.” Thank you, Kevin.
Close-together sprinkling of dozens of bright white stars on field of many much fainter stars.
The Beehive star cluster, aka M44. Image via Fred Espenak at AstroPixels. Used with permission.

Star clusters: Globular clusters

Globular clusters are huge, ancient conglomerations of tightly packed stars that orbit in the halo of the Milky Way. The big balls of stars lie much farther away than the open clusters we see. The best known globular cluster for Northern Hemisphere observers, M13, lies in Hercules. This deep-sky target is easy to spot with a small telescope.

Black field with tight cluster of white dots at right center, with objects labeled.
View larger at EarthSky Community Photos. | Fernando Roquel Torres in Caguas, Puerto Rico, captured this beautiful image of the globular cluster M13. Fernando wrote: “It is curious to know that our favorite astronomer and communicator Carl Sagan sent a symbolic signal to this globular cluster from the Arecibo Radio Telescope in Puerto Rico in 1974. You can also see 2 galaxies in this photo. NGC 6207, which is approximately 30 million light-years from our planet, and IC 4617 is approximately 154.2 million light-years away.” Thank you, Fernando!
Antares shines bright among a backdrop of stars, with M4 nearby, seen as a small compact grouping of many faint stars.
Astronomer and photographer Fred Espenak captured this image of Messier 4, with Antares to its left, using a small telescope. Image via Fred Espenak. Used with permission.

Advice for observing deep-sky objects

To see objects in the deep sky that lie in our Milky Way or even farther, you’ll want a dark sky and binoculars or a telescope. Have patience when tracking down these far-flung gems. Wait for your eyes to grow adapted to the dark. Use averted vision if necessary to pick up the dim fuzzies. A good star chart will help you hop your way across the deep sky and to galaxies beyond our own.

Bottom line: Deep-sky objects are targets in space that amateur astronomers often call faint fuzzies. They lie outside our solar system and don’t resolve into pointlike objects as stars do. Deep-sky objects include nebulae, galaxies and star clusters.

October 12, 2021

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