The Milky Way Overhead
By mid-month, the centre of the Milky way will be directly over head by mid-evening. While you really need a dark sky site to appreciate the beauty of Milky Way, SPIRIT can be used to image the seemingly endless number of star clusters and nebulae which populate the area within and near the galactic plane. Unlike deep space objects such as galaxies, all of these targets exist within our home galaxy. Use Stellarium to zoom in on the region around M 20 and you will have several dozen objects to choose from.
August also represents a rare window to image both of the great southern globular clusters, NGC 5139, and NGC 104. To do so you will need to image NGC 5139 early in the evening, as by mid-month it is low in the south western sky. By comparison, NGC 104 is only just rising in the south east, and does not reach imaging altitude until after 10:30pm.
August provides the second ‘perfect month’ to image the Sagittarius nebulae mentioned in last month’s instalment. Advanced users may consider creating a mosaic of several adjacent fields, as most of these targets extend well beyond the field of view of the SPIRIT telescopes. Patience, and good image acquisition and processing skills are required, as well as some luck – August being one of the worst months of the year at providing weather conducive to astronomy.
A Planetary Conjunction
Although not a viable target for SPIRIT, Mars will meet up with Saturn for a stunning conjunction in August 2012. Don’t forget to walk outside and look west early in the evening to see these two paired together. They will be closest on August 15.
August 2012 provides the rare occurrence of two full moons in one month. Known as a “Blue Moon” due to its rarity (as in the expression, “once in a blue moon”) it will be full on August 2nd and August 31st, so deep sky imaging is best undertaken between August 10 and August 24.
The Perth night sky Facing south at 7:30 pm on August 15.
(click on image to enlarge)