This beautiful cluster was riding high in the clear night sky, almost at the zenith. It was the first image of five objects which I obtained during an evening out in the field with my friends from Macarthur Astronomical Society.
The M6 cluster is about 94 million years old. It needs some considerable imagination to see a butterfly shape but if you begin with the two almost symmetrically curved rows of small stars arranged in a v-shape – the antennae – then perhaps you might be off to a good start.
Most of the stars in the cluster are hot B-type stars but the bright orange star is BM Scorpii, an orange supergiant (mag.6) which has exhausted its hydrogen and swollen in size as it converts helium into heavier elements. It lies in front of the cluster at about 790 light years distance – about half the distance to the cluster. Despite being a supergiant, it is a K2 star which is cooler than our G2 Sun.
There was great excitement amongst our hardy group of astronomers at the news that a bright comet P/2008 Y12 (SOHO) had arrived in the sky.
However, I had other targets in mind – and I’m glad I did, because my friends spent much of the evening searching for it, to no avail. It clearly was much dimmer than the predicted 10th magnitude, which is not uncommon.
After seventeen minutes of this first image, my mount stopped tracking, so here it is – a seventeen minute image of the Butterfly Cluster.
Unfortunately, I had hardware/software/gearware problems which resulted in imaging for shorter durations than I intended but taking a couple more objects (five instead of three) – with a resultant reduction in quality.
The other images will no doubt follow.
Designation: Messier 6, M6, Butterfly Cluster.
Visual magnitude: +4.2
Apparent size: 20′ x 20′
Diameter: 9.2 light years.
Distance: 1,600 light years.
Altitude during exposure: 82° above W. horizon.
My previous image of M6.
Exposure: 12 x 86.2 sec = 17.25 min.
Image acquisition: SharpCap.
|Telescope:||SkyWatcher Esprit||Type:||120ED triplet refractor|
|Focal:||840 mm F/7||Mount:||SkyWatcher EQ6-R Pro|
|Camera:||ZWO ASI 071 MC Pro
||Type:||CMOS 28.4mm 16 Mpx
|Optical aids:||Flattener: Y; filter: N||Guiding:||No|
|Polar aligning:||QHYCCD PoleMaster||Polar Error:||00’ 19”|
[ZWO ASI071MC Pro]
Auto Exp Max Exp M S=30000
Image © Roger Powell