M7, Ptolemy's Cluster, in BinoSky, a guide to astronomy with binoculars.


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M7, Ptolemy's Cluster, in Scorpius

A map of the star field. Magnitudes are given without a decimal point, e.g. 67 is to be interpreted as magnitude 6.7.

Comments
A glorious highlight of the summer sky through binoculars. Very bright, and easily seen even from urban areas. A rich central area containing a prominent cross shape is surrounded by a looser sprinkling of stars in a witch's hat configuration.

60-degree field of view

Data (Janes, Duke, and Lynga, 1987)

RA 17 54

dec -34 49

total V magnitude 3.3

NGC number 6475

Trumpler class I 3 r

angular diameter 80'

distance 240 pc

age (Myr) 130

integrated B-V .15

observed stars 54

earliest sp. class B8

brightest star 7.0

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	A map of the star field. Magnitudes are given without a decimal point, e.g. 67 is to be interpreted as magnitude 6.7.

	Comments A glorious highlight of the summer sky through binoculars. Very bright, and easily seen even from urban areas. A rich central area containing a prominent cross shape is surrounded by a looser sprinkling of stars in a witch's hat configuration.
60-degree field of view

Data (Janes, Duke, and Lynga, 1987)
RA	17 54
dec	-34 49
total V magnitude	3.3
NGC number	6475
Trumpler class	I 3 r
angular diameter	80'
distance	240 pc
age (Myr)	130
integrated B-V	.15
observed stars	54
earliest sp. class	B8
brightest star	7.0