Corona Australis is a small compact constellation
nestled between Sagittarius and Scorpius, just east of Scorpion's stinger.
The constellation is quite old, and is said to represent the crown worn
by the centaur Sagittarius (and sometimes known as "Corona Sagittarii").
Like a number of other constellations in the southern hemisphere, its
Bayer stars are far from complete, and are
rather faint as well.
Kappa2 and kappa1 Coronae Australis form a
gorgeous fixed double, visible in most of North America (as far north
as Vancouver and Winnipeg) but only part of Europe, generally south
of Paris or Stuttgart, and not at all in the UK.
h5014 is a close visual binary with an orbit
of 191 years. These are two equal stars: 5.7, 5.7. Epoch 2000 values
are PA 346º and separation 0.9".
Kappa2 is the primary: 5.9, 6.6; 359º and separation
Corona Australis has no long-period variables, but there are several
irregular variables of considerable interest. Two of these, TY and R,
are found in the nebulosity NGC 6726/27/29 (see below).
Deep Sky Objects:
There are no Messier objects in Corona Australis, however the constellation
does have a globular cluster suitable for binoculars, as well as an
interesting region of nebulosity that goes under a multiple name.
NGC 6541 is a globular cluster, quite large and bright, about
15,000 light years away. It's nearly midway between theta CrA and theta
Sco, a bit closer to the latter (more precisely thirty arc minutes east of
NGC 6729 is part of a nebulous region that contains both variable
stars R CrA and TY CrA.
The region is a mixture of bright and dark nebulae; the brightest region
is NGC 6726/6727, which form a figure eight. Just to the SE is NGC 6729,
which is much fainter, but of more interest as it contains R CrA, an
irregular variable that goes from 9.7 to about 12. As the star
brightens, so does the surrounding nebula.
The other variable, TY CrA, is found in NGC 6726, and varies from about
8.8 to 12.6.
The easiest way of finding the nebulosity is to drop seven and a half
degrees south of zeta Sagittarii.