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 Last updated 1 May 2007


About the Section

Solar observation is a very rewarding endeavour. The Sun is an interesting object to observe and requires relatively little and cheap equipment. It provides great opportunities for either recreational purposes or involvement in global research projects/networks.

The aims of the Solar Section are therefore to:

  • promote solar observation in Southern Africa
  • to assist the beginner to commence solar observation
  • to coordinate observation programs for the serious observer
  • to provide an information service to the public
  • to maintain contact with a variety of international institutions.

Facts about the Sun

Mass (kg) 1.9891·1030
Diameter (km) 1.392·106
Escape velocity (km·s-1) 617.7
Luminosity (watt) 3.846·1026
Mass conversion rate (kg·s-1) 4.3·109
Spectral type G2 V
Absolute magnitude +4.83
Apparent visual magnitude -26.7
Distance from Earth (km) 1.47-1.52·108
Core pressure (bar) 2.477·1011
Core temperature (°C) 1.571·107
Rotation period (hours) 609.12
Speed relative to nearby stars (km·s-1) 19.4

Bloemfontein Centre's solar web page

Bloemfontein Centre runs a general solar page with more information about the sun and observations: []

South African observers' sunspot diagram. This graph displays the average number of sunspots counted by South African observers since the mid-1990's, up to 2006. This period is also known as "Solar Cycle 23". Submitted by Jacques van Delft, ASSA's Director of its Solar Section.


Solar Bulletins

December 2009: Word | PDF
November 2009: Word | PDF
October 2009: Word | PDF
September 2009: Word | PDF
August 2009: Word | PDF
July 2009: Word
June 2009: Word | PDF
May 2009: Word | PDF
April 2009: Word | PDF
March 2009: Word | PDF
February 2009: Word | PDF
January 2009: Word | PDF

August 2008: Word | PDF
July 2008:
Word | PDF
April 2008: Word | PDF
March 2008
: Word | PDF
February 2008
: Word | PDF
January 2008
: Word | PDF

2007 complete archive: Zip file
2006 complete archive: Zip file 709 kb

2005 complete archive: Zip file 700kb
2004 complete archive: Zip file

Order the Solar CD

"Fun with the Sun!" - all the information you need to start off with your OWN solar observations. Contains solar images, interesting facts and solar data as well as how-to's on solar observations. Cost: R30 (including postage in South Africa). Overseas orders, please request a quote. Send your order and postal details to Jacques van Delft, Solar Section director.

Contact details

ASSA Solar Section Director
Johan Retief
e-mail: [
solar (at)]


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