Object name: M011

Designation(s): M011,

M11 is one of the most famous open star clusters. It is located in the small constellation of Scutum right in the heart of the Milky Way. Normally this would make the cluster rather hard to separate from the background but M11, listed as Trumpler I2r stands out strongly thanks to its high star density. Many open clusters have a couple hundred stars or fewer only a few dozen that they eye sees in a typical scope. But this cluster has about 3000 stars of which 500 are magnitude 14 or brighter and thus seen in an 8 to 10" scope. Even a smaller scope sees a few hundred stars not a dozen or so of many clusters. WEBDA puts it about 6100 light-years distant so it stands in front of most of the stars of the Milky Way in Scutum which I find to be nearly twice that distance on average. It's most massive stars are listed at spectral type B8 meaning it is a rather young cluster. WEBDA puts its age at just under 200 million years. Being young most of its blue stars B8 and less massive are still on the main sequence so the cluster is quite blue even if it is reddened by 0.426 magnitudes according to WEBDA. I didn't try to compensate for that in my image.

Like many of my Messier object images, this one was taken before I really knew what I was doing. In an attempt to better show off the cluster I limited exposure time to only 10 minutes. This does bring out the cluster but it loses the fainter members of the cluster at the same time. I now have ways of doing this via processing that keeps these fainter stars. Also at the time, I was only using G2V color balancing which doesn't do well for dust reddened images. Still, it looks close enough considering the minimal exposure time so I didn't reprocess it in any way from my hack job back in 2007. Instead, it is on my reshoot list which may or may not happen. It is displayed at 1.5" per pixel rather than my normal 1" per pixel.

The cluster is thought to have been first seen by Gottfried Kirch in 1681 though he didn't see any of its stars showing his scope to be rather poor. William Derham is the first known to see stars in it sometime around 1733. Charles Messier recorded it on May 30, 1764.

For more see:

14" LX200R @ f/10, L=5x2' RGB=3x2', STL-11000XM, Paramount ME

Related Designation(s):

M011, MESSIER 011, NGC 6705,