BAS Observer December 2017

DECEMBER 2017 7 Constellation of the month: Eridanus The constellation Eridanus is one of Greek astronomer Ptolemy’s 44 original constellations. Eridanus translates to ‘the River’ and is one of the largest constellations in the sky – but not one of the easiest to locate visually. In Greek mythology the constellation marks the wild path of a runaway chariot, driven by Phaeton as he attempted to guide the Sun across the sky. The easiest place to start when trying to locate Eridanus is at either of its ends. The constellation winds its way from bright star Rigel at the foot of Orion to the reasonably bright star Achernar in the far southern sky. The constellation is best known for its galaxies; however, most are very distant and faint. Galaxy NGC 1300, located 47 million light-years away, is a large, face-on spiral that is worth seeking out. But in a dark sky there are many additional galaxies that are also worth hunting for in Eridanus. There are also some great astrophotography targets, such as the Witch’s Head Nebula. The Moon The Moon will be a little closer to Earth this month – just 357 4 9 2 km away at the time of Full Moon – so it will be designated as another ‘Super Moon’. Prepare to be dazzled at the eyepiece this month! The planets The big, bright planets have all departed, leaving just Neptune and Uranus high in the sky. While both these planets have a slightly blue colour which aids identification, a good set of detailed star charts showing their day-by-day location is a good tool to have available when hunting for these tiny planetary dots in a starry sky. Neptune Uranus Observing target: • NGC 1300 – galaxy