Monitoring advice: Two spherical clusters at a glance
Observing tip for bright nights: In the constellation Ophiuchus we find the globular star clusters Messier 10 and Messier 12, which, with their angular separation of only about three degrees, fit comfortably into binoculars' field of view.
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Using binoculars, deep sky objects can be observed even in bright summer skies.
In the constellation Ophiuchus (Latin: Ophiuchus) we find two spherical star clusters: Messier 10 and Messier 12, both of which, with an angular separation of just over three degrees, lie within the field of view of binoculars. The proximity of the two objects in the sky is not an illusion, because the nests of stars are also adjacent in space and time. Messier 10 is about 14,000 light-years away from us, and Messier 12 is about 1,600 light-years away – both clusters move in similar orbits around the center of the Milky Way system and are among the oldest objects of their kind, forming 11 to 14 billion years ago, when Our galaxy was still there, it did not take its current shape as a disk with a central thickening, but rather a spherical condensation of matter.
In binoculars, Messier 10 and Messier 12 appear as diffuse nebula balls with apparent magnitudes of 6 to 7 mg. Under dark skies, their dark outer areas become more visible; Visually, the two objects are up to ten arc minutes in diameter. The region surrounding both constellations, the constellation Ophiuchus, contains only a few bright stars that can serve as clues when searching (see “Deep-sky objects for bright nights”). It's best to orient yourself towards the bright star Delta Ophiuchi (δ Oph) with a magnitude of 2.7 mg and its southeastern neighbour, the star Epsilon Ophiuchi (ε Oph) with a magnitude of 3.2 mg. From here, pan about seven degrees to the east – this corresponds to approximately one field of view diameter for a standard binocular.
Deep sky objects for bright nights | The globular star clusters Messier 10 and Messier 12 are located about seven degrees east of the stars Delta and Epsilon Ophiuchi (δ and ε Oph), and thanks to their mutual angular separation of only 3.3 degrees, they can be viewed simultaneously in their binocular view.
Messier 12 is located 3.3 degrees northwest of Messier 10. By looking at the two globular groups side by side, the two globular groups can now be compared very precisely binocularly. You'll notice that despite all the similarities, Messier 10 is slightly brighter than Messier 10. Messier 10 is also the larger of the two. Although both clusters are about 80 light-years in diameter, Messier 10 contains about 225,000 solar masses within its volume, while its northwestern companion has only about 90,000 solar masses.
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Something small
What is a minute of arc? When do we talk about pairing? How do you determine the brightness of stars? A brief overview of the most important astronomical terms.
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Minute of arc
A minute of arc is a unit for indicating the size of angles in degrees. A degree of angle has 60 arc minutes and a minute of arc has 60 arc seconds. Therefore, 3600 arc seconds results in exactly one degree.
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Ecliptic
The apparent annual path of the Sun in the sky. It is the intersection of the Earth's orbit, the so-called plane of the ecliptic, with the celestial sphere. The plane of the ecliptic is inclined by 23.5 degrees from the equatorial plane, which is the intersection of the Earth's equator with the celestial sphere.
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elongation
The angular distance between the Sun and a planet or Moon. If the planet is at eastern elongation, it will set after the sun in the evening; If the planet is at western elongation, it will rise before the sun in the morning. An elongation of 0 degrees is called conjunction and 180 degrees is called opposition.
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brightness (as)
For historical reasons, brightness was initially divided into six magnitude classes. The first detector was the human eye, which was certainly not fully developed for astronomical observational purposes. The brightest stars are defined as stars of first magnitude (1 mag), and the faintest, visible only to the eye, as stars of sixth magnitude (6 mag).
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coupling
Equilibrium, the position of the planet in which the Sun is on the line connecting the Earth to the planet. The planets Mercury and Venus have an upper conjunction when the sun is between the Earth and the planet, and a lower conjunction when the planet is between the Earth and the sun.
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Peak
Passage of a star across a meridian. A distinction is made between the upper peak (the greatest height above the horizon) and the lower peak (the greatest height below the horizon). Only the pole stars have their upper and lower zenith points above the horizon.
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longitude
The noon circle, in the horizontal coordinate system, is the great circle of the celestial sphere, which passes through the zenith and perigee as well as through the celestial poles and intersects the horizon at the south and north points.
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opposition
Opposite glare is the angular position of two planets relative to each other or to the Sun and Moon, where the ecliptic longitude of the two stars differs by 180 degrees. It is commonly used when the Sun, Earth, and one of the outer planets are on the same line.
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Vision
– Stars flickering due to atmospheric turbulence.
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