Popular Astronomy

June 2014

Michael Kinns sent in two drawings this month, both of globular clusters.

M12, a globular cluster in the constellation of Ophiucus, is on the left.  Michael reports that the extent of the stellar halo was only apparent after full dark adaptation at 22.30 UT.  The faintest star recorded is magnitude 13.  Michael uses a 200mm f6 Newtonian telescope, which is probably the minimum aperture required to resolve this globular into stars.  M12 is about 15,700 light years from the Earth, and is about 75 light years across.      

On the right is M92,  a globular cluster in the constellation of Hercules.  Michael resolved this globular despite a gibbous moon in the South: the faintest star seen is magnitude 12.  M92 is about 26,700 light years from the Earth and is one of the oldest globular clusters.                                                                                                                                                                                                      

                                                                                                                                                                                                        


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