SOCO IMAGE GALLERY


 

M 6     The Butterfly Cluster 

M 6 (NGC 6405) is a large, bright open cluster lying just above the "stinger" in the tail of Scorpius. This cluster was first observed by Giovanni Batista Hodierna on or before 1654. In his observations, he counted 18 stars. The cluster was later independently discovered by de Cheseaux in 1745 or 1746 and by Louis de Lacaille in 1752. Messier knew of la Caille's observation of this cluster and observed it himself in May of 1764.
Without a doubt, M 6 is one of the finest open clusters that can be observed with binoculars or a small telescope. With a visual magnitude of 4.2, it can easily be seen with the naked eye as a glowing patch separated from the rest of the Milky Way stream. The popular name for the cluster is attributed to Robert Burnham, Jr., who saw in it a butterfly with outstretched wings. In my image, the "wings" stretch out toward the upper left and lower right corners, while the "body" is comprised of several bright stars in the center of the cluster— there is even the indication of the two "antennae" of the insect comprised by two strings of four small stars each that together form a small "V".
M 6 contains around 120 member stars, almost all of which are young blue-white stars of spectral classes A and B. The notable exception is the bright orange-red class K3 star HD 160371 (BM Scorpii) nestled along the left edge of the cluster in my image. BM Scorpii is a variable reaching a maximum visual magnitude of 5.8, at which it becomes the brightest star in the cluster. M 6 has a physical diameter of 10 LY and lies at a distance of 1590 LY, which is almost twice as far away as the neighboring cluster M 7. Its age is estimated at 80 to 100 million years.

Date(s) Acquired: 24, 27 June 2016
Telescope: Orion 120mm EON Apochromatic Refractor
Camera: QSI Model 583 with Optec NextGEN Ultra Widefield 0.7X Telecompressor

 

   Exposure Time (min) 
   Number of Exposures
   RGB
   1.5
   
   -
   
   -
   OIII
   -
   RGB
   16
   
   0
   
   0
   OIII
   0

 

Processing:
Master red, green, and blue images created using SuperSIAM.
Color composite image created using Basic Processing Procedure III.
Color composite image contrast-stretched using Adobe Photoshop.




 

 

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