Editing Binoculars (section)

=== Astronomical ===
[[File:Астрономический бинокль FUJINON 25x150 MT-SX.JPG|thumb|25&nbsp;×&nbsp;150 binoculars adapted for astronomical use]]

Binoculars are widely used by [[amateur astronomy|amateur astronomers]]; their wide [[field of view]] makes them useful for [[comet]] and [[supernova]] seeking (giant binoculars) and general observation (portable binoculars). Binoculars specifically geared towards astronomical viewing will have larger [[aperture]] objectives (in the 70&nbsp;mm or 80&nbsp;mm range) because the diameter of the objective lens increases the total amount of light captured, and therefore determines the faintest star that can be observed. Binoculars designed specifically for astronomical viewing (often 80&nbsp;mm and larger) are sometimes designed without prisms in order to allow maximum light transmission. Such binoculars also usually have changeable eyepieces to vary magnification. Binoculars with high magnification and heavy weight usually require some sort of mount to stabilize the image. A magnification of 10x is generally considered the practical limit for observation with handheld binoculars. Binoculars more powerful than 15×70 require support of some type.  Much larger binoculars have been made by [[amateur telescope making|amateur telescope makers]], essentially using two refracting or reflecting astronomical telescopes.

Of particular relevance for low-light and astronomical viewing is the [[ratio]] between magnifying power and objective lens diameter. A lower magnification facilitates a larger field of view which is useful in viewing the [[Milky Way]] and large nebulous objects (referred to as [[Deep-sky object|deep sky]] objects) such as the [[nebulae]] and [[galaxies]]. The large (typical 7.14&nbsp;mm using 7×50) exit pupil [objective (mm)/power] of these devices results in a small portion of the gathered light not being usable by individuals whose pupils do not sufficiently dilate. For example, the pupils of those over 50 rarely dilate over 5&nbsp;mm wide. The large exit pupil also collects more light from the background sky, effectively decreasing contrast, making the detection of faint objects more difficult except perhaps in remote locations with negligible [[light pollution]]. Many astronomical objects of 8 magnitude or brighter, such as the star clusters, nebulae and galaxies listed in the [[Messier Catalog]], are readily viewed in hand-held binoculars in the 35 to 40&nbsp;mm range, as are found in many households for birding, hunting, and viewing sports events. For observing smaller star clusters, nebulae, and galaxies binocular magnification is an important factor for visibility because these objects appear tiny at typical binocular magnifications.<ref name=ST2012>[[Sky & Telescope]], October 2012, Gary Seronik, "The Messier Catalog: A Binocular Odyssey" (pg 68)</ref>
[[File:Galassia di Andromeda tel114.png|thumb|A simulated view of how the [[Andromeda Galaxy]] (Messier 31) would appear in a pair of binoculars]]
Some [[open clusters]], such as the bright double cluster ([[NGC 869]] and [[NGC 884]]) in the constellation [[Perseus (constellation)|Perseus]], and [[globular clusters]], such as [[Messier 13|M13]] in Hercules, are easy to spot. Among nebulae, [[Messier 17|M17]] in [[Sagittarius (constellation)|Sagittarius]] and the [[North America Nebula]] ([[NGC 7000]]) in Cygnus are also readily viewed. Binoculars can show a few of the wider-split [[binary stars]] such as [[Albireo]] in the constellation [[Cygnus (constellation)|Cygnus]].

A number of Solar System objects that are mostly to completely invisible to the human eye are reasonably detectable with medium-size binoculars, including larger craters on the [[Moon]]; the dim outer planets [[Uranus]] and [[Neptune]]; the inner "minor planets" [[Ceres (dwarf planet)|Ceres]], [[Vesta (asteroid)|Vesta]] and [[Pallas (asteroid)|Pallas]]; Saturn's largest moon [[Titan (moon)|Titan]]; and the [[Galilean moons]] of [[Jupiter]]. Although visible unaided in [[air pollution|pollution]]-free skies, Uranus and Vesta require binoculars for easy detection. 10×50 binoculars are limited to an [[apparent magnitude]] of +9.5 to +11 depending on sky conditions and observer experience.<ref name="binoculars">{{cite web
  |year=2004
  |title=Limiting Magnitude in Binoculars
  |publisher=Cloudy Nights
  |author=Ed Zarenski
  |url=http://www.cloudynights.com/documents/limiting.pdf
  |access-date=2011-05-06
  |archive-date=2011-07-21
  |archive-url=https://web.archive.org/web/20110721072103/http://www.cloudynights.com/documents/limiting.pdf
  |url-status=live
  }}</ref> Asteroids like [[704 Interamnia|Interamnia]], [[511 Davida|Davida]], [[52 Europa|Europa]] and, unless under exceptional conditions, [[10 Hygiea|Hygiea]], are too faint to be seen with commonly sold binoculars. Likewise too faint to be seen with most binoculars are the planetary moons, except the Galileans and Titan, and the [[dwarf planet]]s [[Pluto]] and [[Eris (dwarf planet)|Eris]]. Other difficult binocular targets include the phases of [[Venus]] and the rings of [[Saturn]]. Only binoculars with very high magnification, 20x or higher, are capable of discerning Saturn's rings to a recognizable extent.  High-power binoculars can sometimes show one or two cloud belts on the disk of Jupiter, if optics and observing conditions are sufficiently good.

Binoculars can also aid in observation of human-made space objects, such as [[satellite watching|spotting satellites in the sky as they pass]].