Of Galaxies and Globulars
With the centre of the milky way now well past the meridian at sunset, it’s time to start looking beyond the bright nebulae and clusters that dominated the skies from July to September.
Rising in the east is the magnificent Sculptor galaxy, NGC 253. One of the largest and brightest galaxies in our skies, it fills the field of view of both SPIRIT I and SPIRIT II (check out this image of NGC 253 taken by SPIRIT I in 2011). NGC 253 is one of our closest neighbours in the local group of galaxies and shows areas of intense star formation in its near edge-on spiral arms. October is a great month to plan some long exposures of NGC 253, as it is directly over head at about 10:30pm at mid month. Close to NGC 253 are a number of other galaxies worth targeting, including NGC 247, NGC 55 and the beautiful face on spiral galaxy NGC 300. Longer exposures of up to a minute or more under good sky conditions are required to reveal the detail in these targets.
Meanwhile, high in the south east is the impressive globular cluster NGC 104, better known as 47 Tucanae. It too crosses the meridian mid month at about 10:30pm. The second largest globular cluster in the sky (after Omega Centauri), 47 Tucanae and its nearby smaller companion NGC 362 are located close to another member of our local group of galaxies, the Small Magellanic Cloud.
47 Tucanae is uniquely placed in the southern sky and is the envy of all northern hemisphere observers. Imaging this object is a must for all users of SPIRIT, and relatively short exposures (less than 30 seconds) through the red, green and blue filters can be used to successfully create impressive colour images of this interesting globular cluster.
The Perth night sky facing south at 7:30 pm on October 15th
(click on image to enlarge)