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Contains:  M 71, NGC 6838
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M71, 





    
        

            Bob J
M71

M71

Technical card

Resolution: 3088x2074

Dates:June 21, 2019

Frames:IDAS LPS D2 2": 60x60" (gain: 75.00) -7C bin 1x1

Integration: 1.0 hours

Darks: ~25

Flats: ~50

Flat darks: ~50

Bias: ~50

Avg. Moon age: 18.65 days

Avg. Moon phase: 83.84%

Bortle Dark-Sky Scale: 4.00

Temperature: 23.00

Astrometry.net job: 2771051

RA center: 298.442 degrees

DEC center: 18.777 degrees

Pixel scale: 1.544 arcsec/pixel

Orientation: 359.347 degrees

Field radius: 0.797 degrees

Data source: Backyard

Description

From Wikipedia:

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 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. 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.

Comments

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Space_Oddity
Bob J
License: Attribution-NonCommercial-ShareAlike Creative Commons
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            Bob J
    Original
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            Bob J
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Sky plot

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Histogram

M71, 





    
        

            Bob J