7th November 1631 A transit of Mercury occurs. Many astronomers set up to capture Mercury's movement in front of the Sun. However only one, a catholic priest named Pierre Gassendi, published his observations and revealed for the first time the size of a planet compared to the Sun. Thus, Pierre Gassendi became the first known person to observe a transit of Mercury. He observed the transit in a darkened room by projecting the image of the Sun through his telescope. Initi

In this Issue: The Einstein Ring; Presidential Address at AGM; Secretary's report; Solar Observations; Observing Double Stars; SC25. You can download the Bulletin here:

by Andrew Wood Following a period of unusually low solar activity (the appearance on the Sun’s disc of sunspots), followers of Monty Leventhal’s monthly presentations and articles will be aware that the Sun is starting to become more active. Monty’s equipment is sophisticated, allowing views of the Sun’s granular surface as well as solar flares and sunspots. Without this specialised equipment, however, ordinary telescopes fitted with solar filters can be used to observe -and

The dictionary defines binary as “composed of or involving two things”, so a binary star is a system composed of two stars which orbit each other due to their mutual gravity. You can read Sydney City Skywatcher, Andrew Wood's, observations of double or binary stars here. Binary systems can be formed of stars with different masses and ages, for example, two Sun-like stars, or a giant star and a Sun-like star, or two white dwarfs etc. The most massive binary system known i