M55 (Gary Imm) - AstroBin

Celestial hemisphere: Southern · Constellation: Sagittarius (Sgr) · Contains: M 55 · NGC 6809 · PGC 63441 · PGC 63445 · PGC 63454 · PGC 706982 · PGC 707076 · PGC 707215 · PGC 707455 · PGC 707846 · PGC 708216 · PGC 708277 · PGC 709384 · PGC 714849 · PGC 714972 · PGC 715213 · PGC 715489 · PGC 715539 · PGC 715602 · PGC 716211 · PGC 92549

M55

This object, also known as NGC 6809, is a beautiful globular cluster located 18,000 light years from Earth in the southern constellation of Sagittarius at a declination of -31 degrees. It appears in the sky to be almost two thirds the size of the full Moon.

The cluster contains roughly 100,000 stars. The stars in the cluster are mostly old and reddish. Unlike most other globular clusters, the core does not look spherical but seems to have a “dent” at about the 8 o’clock position. The core is about 13 arc-minutes across which corresponds to a distance of 45 light years.

Note that the core center does not appear to be a brilliant white, like other more famous Messier globular clusters. Sky & Telescope magazine, in an October 2020 article by Alan Whitman, says this in that regard – “Messier 55 is the best of the unconcentrated globulars. In a 13 inch Dob this cluster was huge, loose, and well-resolved with a multitude of sparkles on a prominent background glow.” This cluster seems pretty concentrated to me, but Alan knows a lot more about these clusters than I do. I am sure he is speaking on a relative basis to the other core densities.

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The refractors!
CMOS Imagers
Cloudy Nights
Texas Astronomy
Globular Star Clusters
Takahashi Refractors
ASI 6200 MM Pro

Globular Clusters
Messier Catalog (Complete)

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The “AstroBin Image of the Day and Top Picks”, or IOTD/TP, is a long-running system to promote beautiful, interesting, peculiar, or otherwise amazing astrophotographs, with a focus on technical excellence. Learn more.

Submitted The date and time when you submitted this image for IOTD/TP consideration.	...
Views by Submitters (available since September 19th, 2023) Every image is assigned to 50% of available Submitters. In the event that at least 80% of them don't view the image before its time in the IOTD/TP process expires, it's assigned to the other 50% of Submitters and the process begins anew.
Promotions by Submitters When 3 distinct Submitters promote the image, it moves on to the next stage of the process: evaluation for Top Pick status. This requirement, in addition to anonymization of images and distribution to only a subset of them, prevents biases and ensures that the best images are selected.
Promotions by Reviewers When 3 distinct Reviewers promote the image, it moves on to the next stage of the process: evaluation for IOTD status.
Early dismissal Staff members have a lot of images to inspect on a daily basis, and they can dismiss images if they believe they don't meet the requirements for IOTD/TP selection. If an image is dismissed 5 times, it's removed from the process. This streamlines the process and ensures that any bias present in promotions could be overruled by other staff members.

Status	Advanced success
Started	...
Astrometry.net job	4132204
PixInsight job	IHYH24HAWUR512JYBIE6RWD2XH218Z3K
PixInsight queue size	n/a
PixInsight stage	n/a

RA (center)	19h39m59s.999
RA (top/left)	19h43m33s.620
RA (top/right)	19h36m39s.711
RA (bottom/right)	19h36m24s.447
RA (bottom/left)	19h43m22s.116

Dec (center)	-30°57′53″.33
Dec (top/left)	-30°29′22″.10
Dec (top/right)	-30°25′20″.10
Dec (bottom/right)	-31°26′02″.16
Dec (bottom/left)	-31°30′07″.60

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