Observing

The trans-Neptunian dwarf planet Eris, discovered in 2005, comes to opposition in October. This distant, deep-frozen little world is within the reach of amateur CCD imagers.

Have you ever seen a star completely wink out, disappearing completely from view for a few seconds? On the morning of 10 September there is a great chance to see just that but the event is only visible along a narrow, 90-kilometre path across Northern Ireland and Scotland, with the cities of Glasgow and Dundee on or close to the centre of the path. The path of the asteroid occultation cuts across central Scotland, Northern Ireland and into the Republic of Ireland, with Glasgow and Dundee near the centre line. On 10 September at around 3.06am the star HIP 22792, shining at magnitude +7.6, will be occulted by the asteroid (569) Misa, a mag. +14.6 body with an estimated diameter of 65 kilometres. The asteroid itself is too faint to be seen in apertures under 300-mm (12-inch) but the startling effect it will have on the star will be a brilliant and easy thing to see in binoculars. Knowing the positions of the stars and the brighter, numbered minor planets to a high degree of accuracy, astronomers can calculate when an asteroid (Moon and the planets too) will move in front a star. As Misa occults HIP 22793, the star