Today’s Astronomical Events – August 13th, 2015

The open star cluster Messier 39 is well placed for observation tonight. A relatively large, sparse cluster, it lies some way from Deneb but can be easily seen with binoculars. Through my finderscope (with an 8x magnification) in October 2007, it appeared as a clump of stars, a little misty, with three or four bright stars forming a line in the center. On one occasion it looked like a boomerang with the line of stars running across the middle.

Through a small telescope at relatively low power (35x)  it appeared sparsely scattered with all white or blue-white stars, most quite bright, that gave me the impression of a heart. Even at this magnification it appeared so large that it barely fit within the field of view.

Messier 39 was discovered in 1764 by Charles Messier. Lying at a distance of approximately 800 light years, it is thought to be some 200-300 million years old.

(Click on an image to enlarge. Adapted from 2015: An Astronomical Year, available in Kindle and paperback formats from Amazon in the US, Canada and the United Kingdom.)

Images courtesy of Mobile Observatory.



02:55 UT – The almost new Moon passes Mars. (Mars: 99% illuminated, magnitude 1.7, diameter 3.7”. Cancer, not visible.)

The globular star cluster M2 culminates at midnight tonight. (Magnitude 6.3. Aquarius, all night.)

The open star cluster M39 culminates at midnight tonight. (Magnitude 5.5. Cygnus, all night. See images above.)



Events in bold involve objects and/or events that are visible with the naked eye.

All times are in Universal Time (UTC). To convert the time to your timezone, click here.

2015 An Astronomical Year (Kindle Edition) 2016 An Astronomical Year Paperback Cover 2016 The Night Sky Sights The Astronomical Almanac 2015-2019

2015: An Astronomical Year

2016: An Astronomical Year 2016: The Night Sky Sights The Astronomical Almanac (2015-2019) The Amateur Astronomer’s Notebook (Pocket Edition)

(Kindle & Paperback)

(Kindle & Paperback) (Kindle & Paperback) (Kindle & Paperback)


Amazon – US

Amazon – US Amazon – US Amazon – US Amazon – US
Amazon – UK Amazon – UK  Amazon – UK Amazon – UK

Amazon – UK

Details of all available books across the world can be found here or by visiting the author’s page on Amazon. If you have any comments or questions, please feel free to contact me at astronomywriter “at”

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