Popular Astronomy

August 2017

This month, four section members sent in a total of 8 images and 2 sketches of deep sky objects.

David Davies of Cambridge imaged M11, the Wild Duck open cluster, in the constellation of Scutum (right). This is an aggregation of around 3,000 stars, all about 250 million years old, at an estimated distance of 6,200 light years from the Earth.  It is a good target for observers using 10x50 binoculars, and looks similar to a loose, unresolved, globular cluster.

David used an APM 107mm APO refractor and a QSI 583 mono camera plus red green and blue filters.

Paul Crossland of Liverpool imaged the Iris reflection nebula NGC 7023 in the constellation of Cepheus (below left), also known as Caldwell 4.

                                                                               NGC 7023 is actually the star cluster within the nebulosity;  it is one of these stars, SAO 19158, which is illuminating the surrounding gas and dust.  This object is about 1,300 light years from the Earth and is around 6 light years in diameter.  With an apparent magnitude of 6.8 but large 18 arc minute angular diameter it has a low surface brightness and is best seen with medium to large telescopes.

Paul used a Skywatcher ED80 refractor and a Canon 500D DSLR plus CLS filter for this image.


Steve Norrie of Fife employed an ES 127mm f7.5 refractor and a Starlight Xpress Trius - SX694 mono camera plus colour and narrow band filters to produce 6 images of deep sky objects.  Clockwise from below left are IC 1396, the Elephants Trunk emission nebula in the constellation of Cepheus;  M27 the Dumbbell planetary nebula in Vulpecula;  NGC 5070 the Pelican emission nebula in Cygnus and NGC 6888 the Crescent emission nebula also in Cygnus.





Steve's next two images are both emission nebulae in Cygnus, NGC 7000, the North America nebula (below left) and IC 5146, the Cocoon nebula.  The Cocoon nebula is also known as Caldwell 19, and the star cluster Collinder 470 lies within it.  The nebula is about 4,000 light years from Earth and the star producing the ionizing radiation is reckoned to be only around 100.000 years old.  Surrounding the nebula and going up to the top right corner of this image can be seen part of dark nebula Barnard 168.


Michael Kinns of Eastry sent in two sketches.  Below left is M11, the Wild Duck open cluster in the constellation of Scutum (see above), and to the right is M71 globular cluster in Sagitta.  Until the 1970's M71 was considered to be a dense open cluster, now it is described as a loosely concentrated globular!  Unlike most globulars it relatively rich in elements heavier than Helium and lacks RR Lyrae variable stars common in most globulars hence the confusion.  Modern photometry of M71 however produces  an HR diagram for M71 which is typical of a globular cluster.  It is about 12,000 light years from the Earth and around 9 billion years old. At apparent magnitude 8, it may be seen with binoculars.  Michael used an Orion Optics UK SPX 200 f6 Newtonian reflector at x150.


Dave Finnigan 

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