Popular Astronomy

August 2016

A quiet month, with just one section member contributing four images.  I was able to take deep sky images over two evenings however, increasing the total to ten.

Ian Papworth took images of three planetary nebulae and a globular cluster.  Below left is M76, the "little dumbbell" planetary nebula in the constellation of Perseus.  Next to it is M27, the "dumbbell" in Vulpecula, which is 2.5 magnitudes brighter and about 4 times bigger in angular size, so much easier for visual observers to detect.


Ian's next image, below left, is NGC7662, the "blue snowball" planetary nebula in Andromeda.  A favourite with visual observers, the slightly blue disc may be seen through a small telescope. To the right is M92;  this less well known globular cluster in Hercules is a fine object but with M13 nearby it is sometimes overlooked.


I was able to observe on two nights late in August and took six images with a 305mm SCT and DSI II camera.  Three were of objects in the constellation of Delphinus;  below clockwise are planetary nebulae NGC6905 and globular clusters NGC7006 and NGC6934;  planetary nebula NGC6886 is in Sagitta.

NGC6905 is also known as the "blue flash", and has a central white dwarf star with a temperature of 150,000 degrees Kelvin.  NGC7006 is a distant globular, some estimates place it at over 180,000 light years from the Earth.  NGC6934 is about three times closer to us.  Planetary nebula NGC6886 looks quite starlike in this image, so much so that I've added an arrow to locate it in the starfield.  It is about 10,000 light years away, and the slightly oval brighter inner part captured here is only 2 arc seconds across.                                                                                                                                                 






The remaining two images are below.  Left is NGC6712,  a globular cluster in the constellation of Scutum, and right is Palomar 9, a much fainter globular in Sagittarius.  Palomar 9 is the cluster of faint stars below and slightly to the right of the bright star. 

The Palomar globular clusters were discovered on the first Palomar Observatory Sky Survey photographic plates, in the 1950's.  They are either distant, in the outer galactic halo, or like Palomar 9, nearby average globulars heavily obscured by interstellar dust and gas.                                             


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