Editing Binoculars (section)

== Applications ==

=== General use ===
{{multiple image
   | width     = 107
   | footer    = Compact binoculars with double bridge
   | image1    = Leitz Trinovid 8x20 compact binoculars 3.jpg
   | alt21     =
   | caption1  = <small>[[Trinovid]] 8×20 C folded for storage<ref>{{Cite web |url=https://patentimages.storage.googleapis.com/f3/28/19/f7cf757910cb4f/US4087153.pdf |title=US Patent US4087153A Binoculars with double hinge bridge and resilient biasing |access-date=2022-09-17 |archive-date=2022-09-20 |archive-url=https://web.archive.org/web/20220920170343/https://patentimages.storage.googleapis.com/f3/28/19/f7cf757910cb4f/US4087153.pdf |url-status=live }}</ref></small>
   | image2    = Leitz Trinovid 8x20 compact binoculars 1.jpg
   | alt2      =
   | caption2  = <small>Trinovid 8×20 C expanded for use</small>
  }}
[[File:Tower Optical Binoculars.jpg|thumb|[[Tower Optical]] coin-operated binocular tower viewers]]

Hand-held binoculars range from small 3&nbsp;×&nbsp;10 Galilean [[opera glasses]], used in [[theater]]s, to glasses with 7 to 12 times magnification and 30 to 50&nbsp;mm diameter objectives for typical outdoor use.

Compact or pocket binoculars are small light binoculars suitable for daytime use. Most compact binoculars feature magnifications of 7× to 10×, and objective diameter sizes of a relatively modest 20&nbsp;mm to 25&nbsp;mm, resulting in small exit pupil sizes limiting low light suitability. Roof prism designs tend to be narrower and more compact than equivalent Porro prism designs. Thus, compact binoculars are mostly roof prism designs. The telescope tubes of compact binoculars can often be folded closely to each other to radically reduce the binocular's volume when not in use, for easy carriage and storage.

Many [[tourist attraction]]s have installed pedestal-mounted, coin-operated binocular [[tower viewer]]s to allow visitors to obtain a closer view of the attraction.

=== Land surveys and geographic data collection ===
Although technology has surpassed using binoculars for data collection, historically these were advanced tools used by geographers and other geoscientists. Field glasses still today can provide visual aid when surveying large areas.

=== Bird watching ===
[[Birdwatching]] is a very popular hobby among nature and animal lovers; a binocular is their most basic tool because most human eyes cannot resolve sufficient detail to fully appreciate and/or study small birds.<ref>{{cite web | url=https://www.aao.org/eye-health/tips-prevention/what-does-20-20-vision-mean | title=What Does 20/20 Vision Mean? | date=28 January 2022 | access-date=19 June 2020 | archive-date=21 June 2020 | archive-url=https://web.archive.org/web/20200621005530/https://www.aao.org/eye-health/tips-prevention/what-does-20-20-vision-mean | url-status=live }}</ref> To be able to view birds in flight well rapid moving objects acquiring capability and depth of field are important. Typically, binoculars with a magnification of 8× to 10× are used, though many manufacturers produce models with 7× magnification for a wider field of view and increased depth of field. The other main consideration for birdwatching binoculars is the size of the objective that collects light. A larger (e.g. 40–45mm) objective works better in low light and for seeing into foliage, but also makes for a heavier binocular than a 30–35mm objective. Weight may not seem a primary consideration when first hefting a pair of binoculars, but birdwatching involves a lot of holding up the binoculars while standing in one place. Careful shopping is advised by the birdwatching community.<ref>{{cite web | url=https://www.audubon.org/news/how-choose-your-binoculars | title=How to Choose Your Binoculars | date=18 April 2016 | access-date=19 June 2020 | archive-date=21 June 2020 | archive-url=https://web.archive.org/web/20200621220502/https://www.audubon.org/news/how-choose-your-binoculars | url-status=live }}</ref>

=== Hunting ===
Hunters commonly use binoculars in the field as a way to observe distant game animals. Hunters most commonly use about 8× magnification binoculars with 40–45mm objectives to be able to find and observe game in low light conditions.<ref>Michael Schoby, Mike Schoby, Successful Predator Hunting, Krause Publications Craft – 2003, pp. 108–109</ref> European manufacturers produced and produce 7×42 binoculars with good low light performance without getting too bulky for mobile use like extended carrying/stalking and much bigger bulky 8×56 and 9×63 low-light binoculars optically optimized for excellent low light performance for more stationary hunting at dusk and night. For hunting binoculars optimized for observation in twilight, coatings are preferred that maximize light transmission in the wavelength range around 460-540&nbsp;nm.<ref>{{Cite web |url=http://scopeviews.co.uk/Zeiss7x42Dialyt.htm |title=Zeiss 7×42 Dialyt ClassiC Review |access-date=2022-05-05 |archive-date=2022-05-31 |archive-url=https://web.archive.org/web/20220531180152/http://scopeviews.co.uk/Zeiss7x42Dialyt.htm |url-status=live }}</ref><ref>{{Cite web |url=http://www.holgermerlitz.de/swaro7x42.html |title=Review: 7x42 Swarovski Habicht vs. 7x42 Zeiss B/GA Dialyt vs. 8x42 Docter B/CF |access-date=2022-05-05 |archive-date=2022-04-12 |archive-url=https://web.archive.org/web/20220412005026/http://www.holgermerlitz.de/swaro7x42.html |url-status=live }}</ref><ref>{{Cite web |url=https://binocular.ch/zeiss-dialyt-8x56-b-ga-t/ |title=Zeiss Dialyt 8×56 B/GA T 8×56, Abbe-König, Binoculars |access-date=2022-05-05 |archive-date=2022-06-01 |archive-url=https://web.archive.org/web/20220601032133/https://binocular.ch/zeiss-dialyt-8x56-b-ga-t/ |url-status=live }}</ref><ref name="binocular.ch"/><ref>{{Cite web |url=https://www.optics-trade.eu/en/binoculars/hunting-binoculars/low-light-binoculars.html |title=Low Light Binoculars |access-date=2022-05-05 |archive-date=2022-09-09 |archive-url=https://web.archive.org/web/20220909045434/https://www.optics-trade.eu/us/binoculars/hunting-binoculars/low-light-binoculars.html |url-status=live }}</ref>

=== Range finding ===

Some binoculars have a range finding [[reticle]] (scale) superimposed upon the view. This scale allows the distance to the object to be estimated if the object's height is known (or estimable). The common mariner 7×50 binoculars have these scales with the angle between marks equal to 5&nbsp;[[angular mil|mil]].<ref name="bushnell">{{Cite web |url=http://www.binoculars.com/images/pdf/BUP336.pdf |title=Binoculars.com — Marine 7 × 50 Binoculars. Bushnell |access-date=2009-07-05 |archive-date=2011-09-10 |archive-url=https://web.archive.org/web/20110910153501/http://www.binoculars.com/images/pdf/BUP336.pdf |url-status=live }}</ref> One mil is equivalent to the angle between the top and bottom of an object one meter in height at a distance of 1000 meters.

Therefore, to estimate the distance to an object that is a known height the formula is:

:<math>D = \frac{OH}{\text{Mil}}\times 1000</math>
where:
* <math>D</math> is the ''Distance'' to the object in meters.
* <math>OH</math> is the known ''Object Height''.
* <math>\text{Mil}</math> is the angular height of the object in number of ''Mil''.

With the typical 5 mil scale (each mark is 5 mil), a lighthouse that is 3 marks high and known to be 120 meters tall is 8000 meters distant.

:<math>8000 \text{m} = \frac{120 \text{m}}{15 \text{mil}} \times 1000</math>

=== Military ===
[[File:Leica Vector rangefinder 2007 07 14 n2.jpg|thumb|left|Vector series laser rangefinder 7×42 binoculars can measure distance and angles and also features a 360° digital compass and class 1 eye safe filters]]
[[File:Liverpool Merseyside Maritime Museum 006.JPG|thumb|German U.D.F. 7×50 blc [[U-boat]] binoculars <small>(1939–1945)</small><ref>{{Cite web |url=http://www.binoculars-cinecollectors.com/UDF_by_Anna___Terry_Vacani_-2012.pdf |title=1U.D.F. 7 x 50 blc U-boat sight for torpedo firing By Anna and Terry Vacani |access-date=2020-11-01 |archive-date=2020-11-07 |archive-url=https://web.archive.org/web/20201107080021/http://www.binoculars-cinecollectors.com/UDF_by_Anna___Terry_Vacani_-2012.pdf |url-status=live }}</ref>]]

Binoculars have a long history of military use. Galilean designs were widely used up to the end of the 19th century when they gave way to porro prism types. Binoculars constructed for general military use tend to be more rugged than their civilian counterparts. They generally avoid fragile center focus arrangements in favor of independent focus, which also makes for easier, more effective weatherproofing. Prism sets in military binoculars may have redundant aluminized coatings on their prism sets to guarantee they do not lose their reflective qualities if they get wet.

One variant form was called "trench binoculars", a combination of binoculars and [[periscope]], often used for artillery spotting purposes. It projected only a few inches above the parapet, thus keeping the viewer's head safely in the trench.

Military binoculars can and were also used as measuring and aiming devices, and can feature filters and (illuminated) reticles.<ref>{{Cite web |url=http://www.binoculars-cinecollectors.com/U-boat_binoculars_2.pdf |title=U-boat binoculars and other naval binoculars of World War II |access-date=2022-04-10 |archive-date=2016-10-20 |archive-url=https://web.archive.org/web/20161020130152/http://www.binoculars-cinecollectors.com/U-boat_binoculars_2.pdf |url-status=live }}</ref><ref>{{Cite web |url=https://www.liberatedmanuals.com/TM-9-1580.pdf |title=TM-9-1580, Ordnance Maintenance Binoculars and Telescope, US Departments of the Army and Air Force, 11 February 1953 |access-date=10 April 2022 |archive-date=31 May 2022 |archive-url=https://web.archive.org/web/20220531190818/https://www.liberatedmanuals.com/TM-9-1580.pdf |url-status=live }}</ref>

Military binoculars of the [[Cold War]] era were sometimes fitted with passive sensors that detected active [[Infrared|IR emissions]], while modern ones usually are fitted with filters blocking [[Laser beam#As weapons|laser beams used as weapons]]. Further, binoculars designed for military usage may include a [[stadiametric reticle]] in one eyepiece in order to facilitate range estimation.<ref>{{Cite web |url=http://www.schaper.net/binoculars/steiner/m22/ |title=TM 9-1240-403-12 & P, Operator's and Organizational Maintenance Manual (including Repair Parts List), Binocular M22 (1240-01-207-5787), Headquarters US Department of the Army 1987 |access-date=2022-04-10 |archive-date=2020-11-11 |archive-url=https://web.archive.org/web/20201111220223/http://www.schaper.net/binoculars/steiner/m22/ |url-status=live }}</ref>
Modern binoculars designed for military usage can also feature [[laser rangefinder]]s, compasses, and data exchange interfaces to send measurements to other peripheral devices.<ref>{{Cite web |url=http://www.miloptik.se/pdf/160203_Vect_Produktflyer_VECTOR.pdf |title=VECTOR series range finder binoculars product flyer |access-date=2022-04-10 |archive-date=2022-06-01 |archive-url=https://web.archive.org/web/20220601050324/http://www.miloptik.se/pdf/160203_Vect_Produktflyer_VECTOR.pdf |url-status=live }}</ref>

Very large binocular naval [[Rangefinding telemeter|rangefinder]]s (up to 15 meters separation of the two objective lenses, weight 10 tons, for ranging [[World War II]] naval gun targets 25&nbsp;km away) have been used, although late-20th century radar and laser range finding technology made this application mostly redundant.{{citation needed|date=July 2022}}

===Marine===
[[File:Морской бинокль FUJINON 7x50 MTRC-SX.jpg|thumb|7×50 marine binoculars with dampened [[compass]]]]
[[File:US Navy 021206-N-1328C-501 Signalman 3rd Class Tiffany Culereth from Bronx, N.Y., observes ships in the area through binoculars called "Big Eyes.".jpg|thumb|US Naval ship 'Big eyes' 20×120 binoculars in fixed mounting]]

There are binoculars designed specifically for civilian and military use under harsh environmental conditions at sea. Hand held models will be 5× to 8× magnification, but with very large prism sets combined with eyepieces designed to give generous eye relief. This optical combination prevents the image vignetting or going dark when the binoculars are pitching and vibrating relative to the viewer's eyes due to a vessel's motion.<ref>{{Cite web |url=https://www.svb24.com/en/guide/binoculars.html |title=Make the right choice of marine binoculars |access-date=2022-04-10 |archive-date=2021-07-28 |archive-url=https://web.archive.org/web/20210728034807/https://www.svb24.com/en/guide/binoculars.html |url-status=live }}</ref>

Marine binoculars often contain one or more features to aid in navigation on ships and boats.

Hand held marine binoculars typically feature:<ref>{{Cite web |url=https://www.yachtingworld.com/yachts-and-gear/best-marine-binoculars-7-of-the-best-pairs-137229 |title=What to look for in a good pair of marine binoculars |date=27 October 2021 |access-date=2022-04-10 |archive-date=2022-05-31 |archive-url=https://web.archive.org/web/20220531190818/https://www.yachtingworld.com/yachts-and-gear/best-marine-binoculars-7-of-the-best-pairs-137229 |url-status=live }}</ref>
* Sealed interior: O-rings or other seals prevent air and moisture ingress.
* Nitrogen or argon filled interior: the interior is filled with 'dry' gas to prevent internal fogging/tarnishing of the optical surfaces. As fungi can not grow in the presence of an inert or noble gas atmosphere, it also prevents [[lens fungus]] formation.
* Independent focusing: this method aids in providing a durable, sealed interior.
* Reticle scale: a navigational aid which uses a horizon line and a vertical scale for measuring the distance of objects of known width or height – sometimes an important navigational aid.
* Compass: A compass bearing projected in the image. Dampening helps to read the compass bearing on a moving ship or boat.
* Floating strap: some marine binoculars float on water, to prevent sinking. Marine binoculars that do not float are sometime supplied with or provided by the user as an aftermarket accessory with a strap that will function as a flotation device.

Mariners also often deem an adequate low light performance of the optical combination important, explaining the many 7×50 hand held marine binoculars offerings featuring a large 7.14&nbsp;mm exit pupil, which corresponds to the average pupil size of a youthful dark-adapted human eye in circumstances with no extraneous light.

Civilian and military ships can also use large, high-magnification binocular models with large objectives in fixed mountings.

=== 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]].