M6 and M7, are some of the most spectacular open clusters in the heavens to view with binoculars. M6 and M7 seems to be made for binoculars; their large apparent sizes make them hard to fit into a telescope's field of view, but a binocular's wider field easily encompasses both of them at the same time. They lie just above the Scorpion's tail, very low in the south for skywatchers at midnorthern latitudes.
In a dark sky, M6 can be seen with the naked eye as a dim smudge of light against the glow of the Milky Way. Even the most modest binocular turns it into a spangle of starlight, roughly rectangular shaped. Sprinkle in a little imagination and you can picture the rectangle as a pair of starry wings stretching to either side of the cluster's more densely packed center. This distinctive appearance has earned M6 the nickname the "Butterfly Cluster."
The Butterfly carries an orange stellar ember on its eastern wingtip. This is BM Scorpii, a semiregular variable star whose brightness slowly fluctuates between magnitudes 6.8 and 8.7. |
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