General Information

Thank you for your interest in the Johannesburg Centre of the Astronomical Society of Southern Africa.

We are a group of enthusiasts who come from all walks of life and share a common interest in Astronomy, an interest that may deep and intense or slight and superficial - we welcome and cater for all. Some of us own telescopes, some binoculars and some only a pair of sharp eyes with which to view the heavens.

We meet once a month, on the second Wednesday, in the Sir Herbert Baker Library building at the site of the old Union Observatory, 18A Gill Street, Observatory. Our meetings usually take the form of a lecture by a guest speaker, a debate or film show. The Centre's monthly newsletter provides full details of these meetings.

Observing evenings are held at the Observatory on the Friday closest to New Moon, weather permitting, starting at about 20:00. Members of the general public are particularly encouraged to come and look through the Centre's Telescopes.

Once a month around the time of New Moon we hold an observing session at some place outside the metropolitan area where the skies are relatively dark and unpolluted.

Solar Section

The Solar Section makes detailed and regular observations of the Sun and records Sunspots, Solar flares and electromagnetic disturbances. Approximately one third of the world's solar observers are based in Southern Africa !

Comets and Meteors Section

In Johannesburg Centre this section is divided into two parts, comet observations and meteor shower observing sessions.

Computer Section

This section deals with the use of computers in Astronomy.

Lunar Occultations Section

Members of this section make accurate timings of the disappearance and reappearance of stars behind the Moon. These observations are used to refine calculations of the orbit of the moon and the positions of the stars.

Grazing Occultations Section

Grazing occultations are a refinement of normal Lunar occultations where, instead of stars disappearing behind the Moon completely, it just skims the Moon's edge. These events are rarely observed from one's back garden because one has to accurately position oneself on the Earth's surface where the event is to occur, this nearly always results in travelling some distance from home.

Results from these events are used not only to refine the Moon's orbit, but also to map accurately the surface of the Moon in the polar regions (the only places where these events occur). Graze expeditions are usually lots of fun.

Variable Star Section

This section makes observations of stars which, for some numerous reasons, vary in brightness. Some of these variable change brightness in a cyclic fashion aver periods, ranging from days to years, whereas others stay at a fairly constant brightness and then suddenly undergo a very rapid brightening or dimming. The technique most often used in the estimation of the brightness of variables is to compare them with stars of known brightness, using special star charts.

Surprisingly, complex and expensive equipment is not required - many variable star observers make use of binoculars only. There are many thousands of such stars in the sky and professional astronomers rely on the amateurs to inform them of any unusual behaviour of these stars.

Observing variable stars is probably the most important contribution that any amateur can make to astronomy.

To Become a Member

If you would like become a member of the Johannesburg Centre please fill in the attached application form and send it with the appropriate joining and subscription fees to the secretary at the above address.

Enquiries