Constellation: Capricornus

Capricornus is constellation best observed in September when it crosses the meridian typically on September 20.  It is a dim constellation where it’s brightest three stars are of magnitude between 2.8 and 4.1.  The asterism resembles a equilateral triangle with bent sides.

There is just one Messier object, a globular cluster and two double star systems.

Although it is rather faint compared to other zodiacal constellations but has one of the oldest mythical stories in western history.  It is represented as a goat with the tail of a fish.  In Greek mythology this constellation is the goat that suckled the infant Zeus after his mother Rhea saved him from being devoured by his father Cronos.

Welcome to the Capricornus Constellation Report!  This report is for observational amateur astronomers.  This AstronomyLog constellation report gives a description of what can be observed in this constellation.  The objects to observe include Messier objects, globular clusters, planetary nebulae, open clusters and double stars.  See more reports at this Constellation Index.

Finding Capricornus

Capricornus is dim but large and surrounded by well-known and recognizable constellations.  In the evenings of September Aquila, containing the dimmest corner of the summer triangle is to the upper right, while the teapot of Sagittarius is to the lower right.  Aquarius is to the upper left.  The primary asterism of Capricornus is a triangle with broken sides where each side is 20 degrees in length.  That’s a little less than the space between your pinky and thumb extended as far apart as possible and held at arm’s length.

Messier Objects

There’s just one Messier object in Capricornus.  M30 is a globular cluster with a diameter of 12.0 arc minutes and a visual brightness of 6.9.  You can see this with binoculars and a small telescope.  It’s just one hop away from ζ-Capricorni in your finder scope or binoculars.  It’s considered a “Tougher” object in 10x50 or smaller binoculars.

This is often the last object to find in the March Messier Marathon.  During that event, it is very difficult to see in a finder scope in the morning twilight.

Globs and Planetaries

There are two globulars in the AL GC Observing Club.  The first in M30 described above (GC 188).  The second is Palomar 12 (GC 189), a challenge list object.   P12 has a diameter of 2.9 arc minutes and a visual brightness of 11.7.  To see this, you will need a medium to large aperture telescope. 

There are no observable planetary nebulas in Capricornus.

Double Stars

There are two double star pairs in the AL DS Observing Club.  Both are bright, well separated and not particularly difficult.

Α-Capricorni (DS 88) is a widely spaced optical double.  It’s possible to separate this pair naked eye.  They are easily separated in binoculars or small telescope.  (sep: 381”, α¹ mv3.6, α² mv4.3).

Β- Capricorni (DS 89) is a widely spaced binary star.  They can be separated in binoculars or small telescope.  (sep: 207”, α¹ mv3.2, α² mv6.1).  This pair has distinct color where the primary is reported to be brilliant yellow and the companion a blue-white.

Open Clusters

There are no observable open clusters in Capricornus.

Summary Nebulae, Galaxies and Clusters

Summary Multiple Star Systems

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