Challenge #4 – C78, Globular Cluster in Corona Australis
| Target | Type | R. A. | Dec. | Constellation | Magnitude | Size |
| C78 (NGC 6541) | Globular Cluster | 18h 08m 02s | -43° 42′ 54″ | Corona Australis | +6.3 | 15.0 arcmin |
Overview
Discovered in 1826 by both Nicolò Cacciatore and James Dunlop independently and is large and bright enough to be seen with binoculars.
As with other Caldwell objects with catalog numbers between 70 and 80, this one never rises more than 10° over the southern horizon for observers in mid-northern latitudes.
This rich cluster is 25,000 light-years from the sun, is about 13 billion years old, and has the mass of about half a million suns. Many astronomers believe it has undergone core collapse, where the mass of stars causes them to fall to its center under gravity.
Finder Charts
This first finder chart shows the sky at 10 pm in the middle of August and contains stars to magnitude five. The moon and planets are not shown.
The globular cluster is marked with a green circle and tagged as NGC 6541. The easiest constellation to identify for the start of the hunt is the teapot shape of Sagittarius, which is circled in orange.
Use the ‘spout’ of the teapot to locate the string of three bright stars in the tail of Scorpius: Shaula, Girtab and Iota1 Scorpii. Follow this line of stars and continue it in the same direction and for a similar distance to land at C78.
This last chart has stars to magnitude seven and the journey to C78 is much clearer. Note the magnitude 4.9 star HR 6682 midway between Iota1 Sco. and C78. This helps us keep on track to the desired object.
In the last section, you’ll discover what you can see of this stunning cluster.
Individual Telescope Views
The following views will help you find C78 in different telescope types by presenting the images as your telescope will show them. The first image is with a black sky and white stars, the second picture is the same image but presented in inverse monochrome. Stars are shown to magnitude 10.0 and the stars in [C78-3] are more clearly shown.
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
Observation
Even at low magnification you’ll see a crisp view of this cluster although you’ll need averted vision to tease out individual suns on the periphery of the cluster.
Higher magnification highlights structure in this world of suns. Now loops and chains of stars appear and the sense of a faint halo expanding away from the core show.
This is an object that relishes high magnification to show off the resolved stars of the outer core but yet we still can’t quite peer into its dense heart.
All in all, this is a stunning view that we can spend many an evening enjoying.
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 [C78-1], for example, click the ‘download’ button next to it below and you’ll be able to open it as a printable pdf.