The open star cluster Collinder 464

When observing large celestial objects, a telescope is not always the best option. Depending on the objective, sometimes binoculars are more suitable for this purpose. Thanks to binocular vision they offer very good contrast perception; In addition, such a compact device can be easily transported anywhere. These are the most obvious technical reasons for astronomical applications.

But something else is yet to come. There are celestial objects whose true nature can only be seen through binoculars. Do not you believe it? Then I invite you to a rehearsal. How about we take a look at the northern constellation of the Giraffe (Latin: Camelopardalis)? The open star cluster Collinder 464 has a total brightness of at least 4.2 mag and a large angular extent of about two degrees, corresponding to four apparent full moon diameters (see “Great Unknown”). Actually, such a large object should be very popular, shouldn’t it?

The Collinder 464 cluster, located about 420 light-years away, contains only a few bright members and, due to the wide distribution of its few stars, almost completely eludes telescope visibility. In the vicinity of the bright 5.4 magnitude star HIP 24254, around eight stars with brightnesses greater than 7 mag can be found. To recognize the character of the cluster a proper comparison with the stellar background is necessary, which in turn provides an optics with a manageable sky field of 5 to 7 degrees, so binoculars with a magnification of 10x or even just 7x. But see for yourself!

• In one word

  What is a minute of arc? When do we talk about conjunction? And how is the brightness of stars determined? A brief description of the most important astronomical terms.

• minute of arc

  The minute of arc is a unit to indicate the size of angles in degrees. One degree of angle has 60 arcminutes and the arcminute has 60 arcseconds. Therefore, 3600 arcseconds equal exactly one degree.

• Ecliptic

  The apparent annual path of the sun in the sky. It is the intersection of the Earth’s orbit, the so-called ecliptic plane, with the celestial sphere. The ecliptic plane is inclined 23.5 degrees to the equatorial plane, the intersection of the Earth’s equator and the celestial sphere.

• Elongation

  Angular distance between the Sun and a planet or the Moon. If a planet is in eastern elongation, it will set after the sun in the afternoon; if it is on a western elongation, it will rise before the sun in the morning. An elongation of 0 degrees is called conjunction and 180 degrees opposition.

• shine (like)

  For historical reasons, luminosity was initially divided into six size classes. The first detector was the human eye, which is certainly not fully developed for astronomical observations. The brightest stars were defined as stars of the first magnitude (1 mag), the faintest stars, barely visible to the naked eye, were defined as stars of the sixth magnitude (6 mag).

• conjunction

  Balance, position of a planet in which the sun is on the line connecting the earth and the planet. The planets Mercury and Venus have a superior conjunction when the sun is between the earth and the planet, and an inferior conjunction occurs when the planet is between the earth and the sun.

• culmination

  Passage of a star along the meridian. A distinction is made between the upper culmination (highest height above the horizon) and the lower culmination (highest height below the horizon). Only circumpolar stars have their upper and lower culmination points above the horizon.

• meridian

  Noon circle, in the horizontal coordinate system, the great circle of the celestial sphere, which passes through the zenith and nadir, as well as the two celestial poles, and cuts the horizon at the south and north points.

• opposition

  Opposite glare, angular position of two planets with respect to each other or with respect to the Sun and Moon, in which the ecliptic longitude of the two stars differs by 180 degrees. It is most commonly used when the Sun, Earth, and one of the outer planets are aligned.

• Seer

  The flickering of stars caused by the turbulence of the atmosphere.