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Contains:  M 71, NGC 6838
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M71 Globular Cluster, 





    
        

            Jerry Macon
M71 Globular Cluster

M71 Globular Cluster

Technical card

Resolution: 3240x2260

Dates:Aug. 14, 2019

Frames:
Astrodon Gen 2 L 36mm: 80x60" (gain: 99.00) -12C bin 1x1
Astrodon Gen 2 RGB 36mm: 55x60" (gain: 99.00) -16C bin 1x1

Integration: 2.2 hours

Avg. Moon age: 13.85 days

Avg. Moon phase: 99.06%

Bortle Dark-Sky Scale: 4.00

Temperature: 10.00

Astrometry.net job: 3021354

RA center: 298.445 degrees

DEC center: 18.789 degrees

Pixel scale: 0.701 arcsec/pixel

Orientation: 358.067 degrees

Field radius: 0.385 degrees

Locations: Dark Star Observatory, Taos, New Mexico, United States

Data source: Own remote observatory

Remote source: Non-commercial independent facility

Description

Images from the following two scopes (piggybacked) contributed to this image:
AG12+ASI1600MM at .70 asec/pix (RGB)
TV127is+ASI183MM at .75 asec/pix. (L)
They were all registered to the best R image taken on the AG12.
Using L from the TV NP127is refractor effectively eliminates the spikes from the AG12.
This image was unguided.

Messier 71 (also known as M71 or NGC 6838) is a globular cluster in the constellation Sagitta. It was discovered by Philippe Loys de Chéseaux in 1745 and included by Charles Messier in his catalog of non-comet-like objects in 1780. It was also noted by Koehler at Dresden around 1775.

The star cluster is at a distance of about 12,000 light years away from Earth and spans some 27 light years across. The irregular variable star Z Sagittae is a member of this cluster.

M71 was long thought (until the 1970s) to be a densely packed open cluster and was classified as such by leading astronomers in the field of star cluster research due to its lacking a dense central compression, and to its stars having more "metals" than is usual for an ancient globular cluster; furthermore, it lacks the RR Lyrae "cluster" variable stars that are common in most globulars. However, modern photometric photometry has detected a short "horizontal branch" in the H-R diagram of M71, which is characteristic of a globular cluster. The shortness of the branch explains the lacking of the RR Lyrae variables and is due to the globular's relatively young age of 9-10 billion years. The relative youth of this globular also explains the abundance of "metals" in its stars[citation needed]. Hence today M71 is designated as a very loosely concentrated globular cluster, much like M68 in Hydra. M71 has a luminosity of around 13,200 Suns.
(Wikipedia)

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Author

jmacon
Jerry Macon
License: Attribution Creative Commons
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M71 Globular Cluster, 





    
        

            Jerry Macon