Extrinsic variables have variations in their brightness, as seen by terrestrial observers, due to some external source. One of the most common reasons for this is the presence of a binary companion star, so that the two together form a binary star. When seen from certain angles, one star may eclipse the other, causing a reduction in brightness. One of the most famous eclipsing binaries is Algol, or Beta Persei (β Per).

VSS runs a number of projects related to eclipsing binary systems, which are outlined below.

• V0454 Carinae spectroscopic and photometric campaign
• QZ Carinae
• Eclipsing Binaries – Insight into Stellar Evolution
• BL Tel Project

Older archived projects can be found here:

• Southern Eclipsing Binaries – EB and EW Project
• Southern Eclipsing Binaries – EA Project
• Southern Binaries DSLR Project
• Equatorial Eclipsing Binaries Project