M68, Globular Cluster in Hydra
| Target | Type | R.A. | Dec. | Constellation | Magnitude | Size |
| M68 | Globular Cluster | 12h 39m 28s | -26° 44′ 39″ | Hydra | 7.84 | 11.0 arcmin |
Overview
This is a beautiful springtime sight in any pair of binoculars or low power field of view.
When Messier discovered it in April 1780, he noted it as being a “Nebula without stars.” When you observe it, you’ll realize how much this statement tells you about the quality of the optics he had to deal with back then.
The New General Catalog description for the same object specifically calls out the “well resolved, stars of magnitude 12.” And it’s right, you will resolve stars in the cluster, perhaps even down to the bright core, so long as you have more than 4″ of aperture to play with.
Containing at least 100,000 stars, this is a large cluster. It shines just brighter than magnitude 8, making it an easy find in all telescopes, and covers an area of sky equivalent to Venus when it is at its farthest from us. In reality, these stars are 33,000 light-years away and occupy and occupy a rough sphere with a diameter of just over 100 light-years.
Let’s discover where to find this pleasing yet low-in-the-southern-sky ball of suns.
Finder Charts
The highest we’ll see this cluster from mid-US latitudes is about 25° over the southern horizon. The further north you live, the lower in the sky M68 appears, so it is not an easy find for Canadians, Scots, or Alaskans.
The first SkySafari 6 star map shows its general location. Pinning it down exactly is best done using the brighter stars of Corvus, the crow. To find Corvus, use the bright stars Arcturus in Boötes and Spica in Virgo to swing down to it. The view below is late evening in the middle of April and stars are shown to magnitude 5.0.
When you’ve located Corvus, M68 is as simple as joining the stars Algorab (Delta Corvi) and Kraz (Beta Corvi) and then extending that line onwards for about half of the same distance again.
When you have it in your eyepiece, M68 will look something like the image below. Keep in mind that this is generated from an astrophoto, what you see in your eyepiece will not be as distinct as this. Stars are shown to magnitude 12.0.
Individual Telescope Views
The following views will help you find M68 in different telescope types by presenting the images as your telescope will show them. Stars are shown to magnitude 12. The first image is with a black sky and white stars, the second picture is the same image but presented in inverse monochrome. Black stars on a white background is often easier to use at the telescope. Each image can be clicked on for a full-screen version.
Upright View – This is what your eyes see unaided and through a reflex or red-dot finderscope
Upside-down view – This is what reflectors and magnifying finders show, and refractors / Cassegrains without a star diagonal
Mirrored View – Refractors and Cassegrain models with a star diagonal show this view
With this bright cluster now in your eyepiece, what should you expect to see?
Observation
The brightest part of the cluster is its core. This world of suns has a mottled appearance and doesn’t need huge magnification to tease out some of its details.
Outside the core, you’ll see plenty of resolvable stars, many of them are twelfth magnitude and within easy reach of most backyard telescopes.
Because this is a globe of bright pinpricks of light, it will tolerate higher levels of magnification. Don’t be afraid to turn the dial up by using a smaller eyepiece and see how close to the center of this cluster you can resolve individual stars.
This cluster is thought to be about 10 billion years old and the stars you are staring out make our sun look like a teenager.
PDFs for Printing
Each of the star maps above is reproduced as a pdf below. Each star map has a number in [square brackets] beneath it which corresponds to the file number below. If you want image [M68-1], for example, click the ‘download’ button next to it below and you’ll be able to open it as a printable pdf.