Arc minutes. There are 60 minutes (denoted as 60') of arc in 1 degree. In the sky, with an unobstructed horizon (as on the ocean), one can see about 180 degrees of sky at once, and there are 90 degrees from the true horizon to the zenith.
arc minutes, and arc seconds are simply ways to measure the size and position of objects in the universe. An arc degree is usually written as 1°, 1 arc minute is denoted by 1', and 1 arc second is 1".
Being 16 arc minutes in length, it has the largest apparent length of any edge-on galaxy discovered.
Coma Star Cluster (Melotte 111)
The Coma Star Cluster is a small star cluster with about 40 bright stars of magnitudes between 5 and 10. The stars in the cluster share a common proper motion.
One degree of arc is defined as equivalent to 60 minutes of arc (or "arc minutes"). Arc minutes are further divided into arc seconds, such that there 60 x 60 or 3600 arc seconds per degree. So the moon's apparent size can also be expressed as 1/2 degree x 3600 = 1800 arc seconds.
How large is the Moon if its angular size is about 30 arc minutes and it is 384,000 kilometers away from us?
How many times biggger is the Sun than the Moon if the Sun is about 390 times farther away than the Moon but has the same angular size? What is the Sun's diameter in kilometers?
Comets - In the case of comets, we speak of a magnitude that is "integrated" over an observed coma diameter of several ~; this is called the comet's "total (visual) magnitude", and is usually denoted by the variable m1.
A telescope's viewing area, measured in degrees, ~, or arc seconds. A telescope that can just fit the full moon into its complete viewing area has a field of view of roughly 30 ~.
Field of view
The field of view is the area of the sky visible through a telescope.
The tidal radius of M3 is about 38 ~.
Mass segregation and luminosity ...
The Sun's apparent size in our sky is 32 ~ (it is the biggest object in the sky - 1 arc minute larger than the moon).
THE MASS OF THE SUN
The Sun's mass is roughly 1.99 x 1030 kg. This is about 333,000 times the mass of the Earth. The Sun contains 99.
The Sun, as it turns out, has an apparent diameter of about 32 ~ (a minute is equal to 1/60th of a degree; a second of an arc is equal to 1/60th of a minute). Another unit of angle is the radian which is the angle that gives an arc of a circle equal to the radius.
Even more interesting are anisotropies at a level of roughly 1/100000 and on a scale of a few ~. Those very small variations correspond to the density fluctuations at the last scattering surface and give valuable information about the seeds for the large scale structures we observe now.
The fourth magnitude star Alcor can be seen at 12 ~ separation from Mizar, corresponding to a projected distance of more than 0.25 ly. However, since Alcor is about 3 ly farther from the earth than the Mizar system, it is unlikely that Alcor is a part of the Mizar system.
It's located at RA 3:47, DEC +24.07 with a visual brightness of 1.6, and apparent dimension of 110.0 ~.
The Hyades, also known as Melotte 25 can be found at RA 4:27, DEC +16 with a visual brightness .5 magnitude and apparent dimension of 330 ~.
It would be ridiculous to measure its size of p with degrees or ~, since p is usually so small. Instead it is always measured in arc seconds (remember one arc second is 1/3600 of a degree, a very small angle indeed).
NGC 1502 is found half way between alpha and beta Cam, and about 55 ~ west. The brightest star in this group is the primary of Struve 485, found at the centre. The binary's vital statistics are AB: 6.1, 6.2; PA 304 degrees, at separation 18.1".
The field of view is usually specified as an angle that depends on the size of the sensor. For example, a lens or telescope of 500mm focal length will cover a field of view of 4 degrees, 17 ~, 43 arc seconds by 2 degrees 51 ~, ...
NGC 3169 and NGC 3166 are compact spiral galaxies lying about 50,000 light-years away from each other, or 7 ~ apart, which is close enough for them to affect each other's structure. NGC 3169 is an active star-forming region, while NGC 3166 is not.
Satellites: The most well-known satellites or companions to M31 are Messier 32 and Messier 110 (also known as NGC 205). These are usually visible in most published images of M31, with the more compact appearing M32 located 22 ~ south of the nucleus of M31, ...
In contrast, the diameter of the Sun on the sky is 32 ~, the diameter on the sky of Venus at inferior conjunction is 1 arc minute,2 the diameter on the sky of Jupiter at opposition is 47 arc seconds,3 and the diameter on the sky of Ganymede, Jupiter's largest moon, at opposition is 1.
Many new stargazers have trouble understanding our reference to 'degrees', '~', and 'arc seconds' when talking about the separation of celestial objects. So here's a primer on measuring angular distances.
A unit of angular measure equal to 60 ~ or 3600 arc seconds. One degree is equal to the diameter of two full Moons.
The amount of mass per unit of volume.
Angular distance is expressed in degrees, radians, ~ (one-sixtieth of a degree), or arc seconds (one-sixtieth of a minute).
Astronomers can measure angles in degrees, ~, arc seconds, or radians. One advantage of using radians is that: ...
The apparent size of an object as seen by an observer; expressed in units of degrees (of arc), ~, or arc seconds. The moon, as viewed from the Earth, has an angular diameter of one-half a degree.
NGC 7318 A and NGC 7318 B are located a few ~ to the northwest of NGC 7320 and taken together they appear nearly as large as NGC 7320 in the eyepiece. The two final members, NGC 7319 and NGC 7317, can be found northeast and respectively southwest of the NGC 7318 pair.
3,900 light-years from us, the NGC 2346 lies in the constellation Monoceros; this image covers approximately 2.8 ~ down, and the nebula is about 0.3 light-years in diameter. The image was originally taken on March 6, 1997, for a total exposure time of 24 minutes.
As the parallax angle for even the nearest stars is very small we use the unit arcsecond (also written as arcsec, as or "). There are 60 arcsecs in 1 arcminute and 60 ~ in 1 degree of arc.
âˆ´ 1 arcsec = 1/(60x60) = 1/3600th of a degree.
A unit of angular measurement. One arc minute is 1/60th of a degree. Just as there are 60 minutes in one hour of time, there are 60 ~ in a one-degree angle.
It is about 70 light-years in diameter and lies about 16,000 light-years from Earth. With a visual magnitude of 6.6 and an apparent diameter of 15 ~, this is one of the best clusters to be viewed with both binoculars and small telescopes. Image credit: Two Micron All Sky Survey (2MASS) ...
A unit of measurement that describes the apparent angular size of an object. It is equivalent to one sixtieth (1/60) of a degree. The angular size of the Moon is about 30 ~.
Perhaps the most interesting thing to see here in Caelum is the variable star R Caeli, a Mira-type long period variable, from 6.7 to 13.7 magnitude every 391 days. It's located one degree south of beta Caeli, and several ~ west.
Future fine-scale experiments designed to map the fluctuations in the cosmic microwave background radiation with an angular resolution of a few ~ are expected to detect large numbers of Sunyaev-Zel'dovich contributions from individual clusters.
Some 40 years later, in 1718, he discovered the proper motion of the hitherto presumed "fixed" stars after comparing his astrometric measurements with those given in Ptolemy's Almagest. Arcturus and Sirius were two noted to have moved significantly, the latter having progressed 30 ~ ...
with other identification and NGC/IC number Type Seyfert type (1, 2); "--" indicates that these are no more classified as Seyfert galaxies RA, Dec Right Ascension and Declination (J 2000.0) Hubble Type Hubble Type m_v Apparent visual brightness in magnitudes Dim Apparent dimension in ~ ...
See also: What is the meaning of Arc minute, Sky, Astro, Star, Earth?