August 2011
The skies cleared in early July courtesy of the fierce winds and I took advantage of the long nights to catch up with my observing.
I won’t spend much time on the planets this month as Jupiter is still an around- midnight proposition (rising around 2AM throughout July) leaving Saturn our prime planetary target. Saturn is still making a nice “yellow” pair with Porrima (γ Virginis) and is worth even a naked eye look each evening to note their gradual separation.
Remember Porrima is a beautiful double star in its own right, here’s an easy way to find one if you’ve never seen a double star before. Saturn will be setting at 10 p.m. at the beginning of August and 9 p.m. by the end so take every chance you can to view this stunning spectacle.
Right at the end of July no less than three meteor showers take place and all peak between the 28th and 31s t .
Opportunely this year the peaks occur at time of New Moon but all showers are better observed after midnight!
In order of peaks they are the Piscis Austrinids, the Southern delta-Aquarids, and the alpha-Capricornids.
Meteor showers are named for the location of their apparent radiant point, i.e. trace the path of the meteors “back” and the radiant is the point where the paths appear to intersect.
All three of these constellations rise approximately due east after midnight so it is quite a feat of observation to differentiate the overlapping showers.
Many years of observation have yielded the common features of the meteors and they are outlined in detail on page 46 of Astronomy 2011.
Comparing them would be a great observing exercise!
This month we continue our deep sky star hopping.
The first target for those with telescopes is an exquisite planetary nebula NGC 3918, the “Blue Planetary”.
Use the arm of Crux to point to this object and use averted vision to get the best result.
Any telescope of 100 mm or better will do, a refractor especially.
Planetary nebulae carry that name for their shape, this one is the spitting image of Uranus. Coincidentally Uranus was discovered by Sir William Herschel and the planetary by his son John.
Following the arm of Crux, the Blue Planetary looks exactly like a hazy blue light bulb!
Blue Planetary, NGC 3918
While in this area turn your telescope or binoculars to the Jewel Box cluster near the left arm of Crux or scan to the west for the beautiful eta Carinae Nebula.
You could also try again for Omega Centauri, the map should help you. From Crux move east using the Pointers, alpha and beta Centaurito find the the constellation Ara, the Altar. In ancient lore it was sometimes described as the Censer or incense burner, the wide crescent of stars in the east forming the bowl of the crucible. On a moonless night you can see what appears to be a large plume of smoke (the Milky Way) rising from the well. For those with a telescope, (200mm would be good), look for the two deep sky objects in Ara, globular cluster NGC 6397 and Planetary NGC 6326.
For naked eye observers enjoy this picturesque asterism and the mystical wisps of smoke that connect you to the ancient observers in Babylon and Mesopotamia.
Ara, the Altar - Clear Skies