Popular Astronomy

July 2015

This month, two section members submited a total of four images.

David Davies imaged M5, a globular cluster in the constellation of Serpens Caput (right).  M5 is close to the star 5 Serpentis, a magnitude 5 star, also in this image.

M5 is magnitude +5.7 (fainter according to some sources) and is definitely non - stellar in binoculars.  A 150mm diameter telescope should resolve this globular intoindividual stars. M5 is about 30,000 light years from the Earth and is considered to be 10 to11 billion years old.  Its apparent size in the sky is around 20 arc minutes;  its actual radius is about 80 light years.

David used a 10'' f4 Newtonian telescope, QSI 583 camera, LRGB filters and a Lodestar off - axis guidance system.               


Ian Papworth sent in three images to Deep Sky section.  On the left, below, is M27, the "Dumbbell" planetary nebula which is in the constellation of Vulpecula (Latin for "little fox).  With an apparent magnitude of  +7.5 it is an easy object in binoculars:  from gamma Sagitta (the tip of the arrow) go up about 3 degrees.  M27 has an angular size of 8 x 5 arc minutes.

Ian's second image (below left) is M14, which is an apparent magnitude +7.6 globular cluster in the constellation of Ophiucus. It is considered to be about 33,000 light years from Earth, with a luminosity of around 400,000 times that of the sun such that it has an absolute magnitude of around -9.    

Ian's third image (below right) is of the planetary nebula M76, the "little Dumbbell", which is in the constellation of Perseus.

This object has an apparent magnitude of +10.1 and is small,    2.7 x 1.8  arc minutes in angular size, so requires a small telescope to see it.  Using averted vision should help.

The hot (80,000 or more degrees Kelvin) star at the centre of M76 whose prodigious output of UV radiation is shaping the nebula has an apparent magnitude +15.9;  estimates of distance vary such that M76 could be between 2,500 and 3,500 light years from the Earth, indeed it is approaching us at about 20 km/second. 

  Ian used a Celestron 6SE f6.3 Schmidt Cassegrain telescope with a ZWO ASI 120MM camera plus filter wheel.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               


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