News / Fun Facts

Atmospheric seeing

Written by: Annarien Bester, SALT intern If you look with your naked eye at the night sky, you will see twinkling objects, most being stars. This twinkling is caused by atmospheric disturbances in the earth’s atmosphere. The higher the disturbance, the more the light from a star is blurred, and the image we observe looks […]

Astronomical twilight

This is the time of day when the sun has either set or is about to rise, but the sky is still being lit by its rays. At SALT we start our evening shift at sunset, preparing for the night ahead, but we only start taking science observations at the end of evening twilight. There […]

Astronomy vs Astrology

This is one that people often seem to confuse, despite their being extremely different. Astronomy, simply put, is the study of objects in space – like stars, galaxies and planets. Astrology is the interpretation of how the movement of celestial bodies might affect the lives of people. When someone comments ”you’re very curious, you must […]

Mirror alignment

SALT has 91 mirrors that work together as ‘one’ 10 metre diameter mirror. Every evening ‘mirror alignments’ need to be done to make sure that all the segments create a uniform spherical surface. The mirror alignment is done using an instrument located in the “Center of Curvature Alignment System” (CCAS) tower. The structure and dome are […]


Every week two mirrors are removed, cleaned and re-coated with aluminium. That way the whole array will be cleaned within a year. The mirror crew are so effective that they’ll sometimes do as many as six in a week.