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Messier 11 and Scutum Star Field

Messier 11 is a beautiful and dense open cluster in the Constellation of Scutum.  Messier 11 is also known by the New General Catalog designation of NGC 6705.  This wide field image shows a the densely packed open cluster, a dense background star field and areas  of dark nebula.  The first recorded observation of the Messier 11 open cluster was by the German astronomer Gottfried Kirch in 1681.  The first astronomer to realize that Messier 11 was made of densely packed individual stars was the English astronomer William Derham in 1733.  Charles Messier added the cluster to his catalogue on May 30, 1764.

Messier 11 can be seen without binoculars or telescopes under very dark skies as a bright patch just north of the Messier 24 star cloud.  It is an easy object for binoculars and a spectacular sight with moderately sized amateur telescopes.  It contains approximately 2,900 individual stars, which makes it one of the most densely packed open clusters that we know of.  Astronomers estimate that the cluster was formed about 220 million years ago.  It is believed to be 6,200 light years away from us.

This image was taken on the night of June 13, 2018 at the San Diego Astronomy Association observing site at Tierra del Sol, San Diego County, California.  Red, green and blue filtered images were used to create the color image.  The telescope was the Stellarvue SV70T with the dedicated 0.8x flattener/reducer.  The camera was the ZWO ASI1600MM-Cooled with the gain at 76 and the offset at 15.  I took 3.5 hours of exposures – 20 each at 210 seconds for the red, green and blue filtered subexposures.

The subexposures were calibrated, aligned and stacked in PixInsight.  Both the DrizzleIntegration tool and the LocalNormalization tool were utilized during the stacking process.  The individual color channels were equalized using the LinearFit tool and combined into a color image using the LRGBCombination tool.  The AutomaticBackgroundExtractor tool was used to eliminate some slight light pollution induced gradients.  A histogram stretch was performed with the HistogramTransformation tool and the image was saved as a 16 bit TIFF image for export to Photoshop.  The Photoshop processing was very minor, a little bit of histogram adjustment to reduce a green cast and then cropping and creating JPEG files for export to the web.

The image below is the full frame wide field view.  Click on the image to see a larger version.  A higher resolution version of this image and the other images below can be found on my Astrobin page.

The image below is a higher resolution crop of the center of the field.  Click on the image to see a larger version.  A 4500 x 3400 pixel version is posted here.

The image below is a high resolution crop centered on the Messier 11 cluster which shows the many tiny stars in the cluster as well as in the background.  Click on the image to see a larger version.  A 300 x 2300 pixel version is posted at this link.

Posted in Processing Notes, Star Clusters

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