Hemisphere:  Southern  ·  Constellation: Scorpius (Sco)  ·  Contains:  M 7  ·  NGC 6475
Messier 7 Ptolemy’s Cluster, 



    
        

            L. Fernando Parmegiani
Messier 7 Ptolemy’s Cluster
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Messier 7 Ptolemy’s Cluster

Messier 7 Ptolemy’s Cluster, 



    
        

            L. Fernando Parmegiani
Messier 7 Ptolemy’s Cluster
Powered byPixInsight

Messier 7 Ptolemy’s Cluster

Technical card

Imaging telescopes or lenses: GSO Ritchey-Chrétien 8"

Imaging cameras: QHY9M

Mounts: Skywatcher NEQ6 Pro goto

Guiding cameras: ASI120MM

Focal reducers: Astro-Physics Astro Physics CCD tele compressor CCDT67 - 0.67x Reducer

Software: PixInsight 1.8 Pisinsight 1.8

Filters: Optolong LRGB 36mm


Dates:Aug. 10, 2018

Frames:
Optolong Blue 36mm: 6x120" (12') bin 1x1
Optolong Green 36mm: 6x120" (12') bin 1x1
Optolong Lum 36mm: 25x120" (50') bin 1x1
Optolong Red 36mm: 7x120" (14') bin 1x1

Integration: 1h 28'

Avg. Moon age: 28.46 days

Avg. Moon phase: 1.28%


Basic astrometry details

Astrometry.net job: 2225827

RA center: 17h 53' 45"

DEC center: -34° 47' 6"

Pixel scale: 0.477 arcsec/pixel

Orientation: 268.899 degrees

Field radius: 0.545 degrees


Resolution: 6588x4932

Data source: Traveller

Description

Messier 7 (M7), also known as Ptolemy’s Cluster, is a bright open cluster in Scorpius constellation.

The cluster lies at an approximate distance of 980 light years from Earth. It has the designation NGC 6475 in the New General Catalogue. With a visual magnitude of 3.3 and an apparent diameter of 80 arc minutes – more than twice the apparent size of the full Moon – Ptolemy’s Cluster is an easy naked-eye target.

Messier 7 can be seen near the stinger of the celestial scorpion. The cluster is the southernmost Messier object in the sky, which makes it a challenging object for those in northern latitudes as Scorpius constellation never rises very high above the horizon.

The best time of year to observe M7 is in the summer months (North Hemisphere) or winter months (South hemisphere). Because of its large size, the cluster is best seen in binoculars.

Messier 7 can be found 4.75 degrees northeast of the star Lambda Scorpii, also known as Shaula.

Shaula marks the scorpion’s stinger and is the second brightest star in Scorpius constellation, fainter only than the red supergiant Antares.

Object: Cluster

Type: Open

Designations: Messier 7, M7, Ptolemy’s Cluster, NGC 6475, Collinder 354, Lac. II.14

Distance: 980 light years (300 parsecs)

Age: 220 million years

Number of stars: 80

Apparent magnitude: 3.3

Apparent dimensions: 80′

Radius: 25 light years

Tidal radius: 40.1 light years

Comments

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Messier 7 Ptolemy’s Cluster, 



    
        

            L. Fernando Parmegiani