The naked eye

The naked eye is a figure of speech referring to human visual perception that is unaided by enhancing equipment, such as a telescope or binocular. A figure of speech, sometimes In Psychology, visual perception is the ability to interpret information from Visible light reaching the Eyes The resulting Perception is also A telescope is an instrument designed for the observation of remote objects and the collection of Electromagnetic radiation. (It, therefore, does not exclude the use of smaller scale aids such as glasses. Glasses, also called eyeglasses or spectacles, are frames bearing lenses worn in front of the Eyes normally for vision correction, ) The term is often used in astronomy when referring to events that can be viewed by the general public, such as astronomical conjunctions, passage of comets or meteor showers. Astronomy (from the Greek words astron (ἄστρον "star" and nomos (νόμος "law" is the scientific study Conjunction is a term used in Positional astronomy and Astrology. A comet is a small Solar System body that orbits the Sun and when close enough to the Sun exhibits a visible coma (atmosphere or a tail — A meteor shower, some of which are known as a "meteor storm" or "meteor outburst" is a celestial event where a group of meteors are observed to radiate from one point Sky lore and various tests demonstrate an impressive wealth of phenomena that can be seen with the unaided eye. Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain

Eye characteristics and everyday life

The basic accuracies of human eyes are:

• Quick autofocus from distances of 10 cm (young people) . Autofocus (or AF) is a feature of some Optical systems that allows them to obtain (and in some systems to also continuously maintain correct focus on a . . 50 cm (most people 50 years and older) to infinity
• Angular resolution: 1–2′ (about 0. Angular resolution describes the resolving power of any image forming device such as an optical or Radio telescope, a Microscope, a Camera 02°–0. 03°), which corresponds to 30–60 cm at a 1 km distance
• Field of view (FOV): simultaneous visual perception in an area of about 130° × 160°
• Faint stars up to +6. The field of view (also field of vision) is the angular extent of the observable world that is seen at any given moment A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth 5 magnitude
• Photometry (brightness) to ±10% or 1% of intensity —in a range between night and day of 1 : 10,000,000,000
• Symmetries of 10–20″ (5–10 cm per 1 km) —see the excellent measurements of Tycho Brahe and the Egyptians
• Interval estimations (for example at a plan on paper) to 3–5%. The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value This article deals with the usage of this term in Optics and Lighting. Symmetry generally conveys two primary meanings The first is an imprecise sense of harmonious or aesthetically-pleasing proportionality and balance such that it reflects beauty or Tycho Brahe, born Tyge Ottesen Brahe ( December 14 1546 &ndash October 24 1601) was a Danish nobleman This article is about the contemporary North African ethnic group
• Unconscious recognizing of movement (that is "alarm system" and reflexes)

Visual perception allows a person to gain much information about his or her environment:

• • the distances and 3-dimensional position of things and persons,
  • the vertical (plumb line) and the slope of plain objects
  • luminosities and colours —and its changes by time and direction
  • . In Physics, motion means a constant change in the location of a body An alarm (French À l'arme - "To the arms" gives an audible or visual Warning of a problem or condition A plumb-bob or a plummet is a weight with a pointed tip on the bottom that is suspended from a string and used as a vertical reference line . . and other qualities of objects.

Naked eye in astronomy

Normally the naked eye can see stars with an apparent magnitude up to +6^m; angular resolution of the naked eye is about 1′ however, some people have a sharper vision than that. The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value There is anecdotal evidence that people had seen the Galilean moons of Jupiter before telescopes were invented. Jupiter has 62 confirmed moons, giving it the largest retinue of moons with "reasonably secure" orbits of any planet in the Solar System Of similar magnitude, Uranus and Vesta had most probably been seen but could not be recognised as planets because they appear so small even at maximum brightness that their motion could not be detected. TemplateInfobox Planet. --> 4 Vesta (ˈvɛstə Vesta is the second most massive object in the Asteroid belt Uranus, when discovered in 1781, was the first planet discovered using technology (a telescope) rather than being spotted by the naked eye. Technology is a broad concept that deals with a Species ' usage and knowledge of Tools and Crafts and how it affects a species' ability to control and adapt A telescope is an instrument designed for the observation of remote objects and the collection of Electromagnetic radiation.

Theoretically, at up to +6^m the human eye would see about 2,500 stars in the clear sky but, in practice, the atmospheric extinction and dust reduce the number to 1500 to 2000 (in the center of a city as few as 200 to 500, due to light pollution). Extinction is a term used in Astronomy to describe the absorption and Scattering of Electromagnetic radiation emitted by Astronomical objects Light pollution, also known as photopollution or luminous pollution, is excess or obtrusive Light created mainly by Humans Among other effects Colours can be seen but just at bright stars and the planets, due to the eye's use of rods instead of cones for fainter stars. A photoreceptor, or photoreceptor cell, is a specialized type of Neuron (nerve cell found in the Eye 's Retina that is capable of Additionally, some star clusters can be detected, such as Pleiades, h/χ Persei, M13 in Hercules, and the Orion Nebula. Star clusters are groups of Stars which are gravitationally bound The Pleiades (ˈpliːədiːz or /ˈplaɪədiːz/ also known as M 45, the '''Seven Sisters''', Seven Stars, SED, Matariki The Double Cluster is the common name for the naked-eye open clusters NGC 884 and NGC 869, which are close together in the constellation Perseus The Great Globular Cluster in Hercules (also known as the Hercules Globular Cluster, Messier Object 13, Messier 13, M13, or NGC 6205 The Orion Nebula (also known as Messier 42, M42, or NGC 1976) is a Diffuse nebula situated south of Orion 's Belt Two of the 18 objects listed in the SEDS Messier catalog as being brighter than +6^m are true galaxies: the Andromeda Galaxy (M31) and the Triangulum Galaxy (M33). The Andromeda Galaxy (ænˈdrɒmədə also known as Messier 31, M31, or NGC 224; often referred to as the Great Andromeda The Triangulum Galaxy (also known as Messier 33 or NGC 598) is a Spiral galaxy approximately 3 million light-years away in the Five planets can be recognised as planets from earth with the naked eye: Mercury, Venus, Mars, Jupiter, and Saturn. In Astronomy, the naked-eye planets are the five Planets of our Solar system that can be discerned with the Naked eye without much difficulty The Sun and the Moon--the remaining noticeable naked-eye objects of the solar system--are sometimes added to make seven "planets. "

Historically, the zenith of naked-eye astronomy was the work of Tycho Brahe (1546-1601), who built an extensive observatory to make precise measurements of the heavens without any instruments for magnification. Tycho Brahe, born Tyge Ottesen Brahe ( December 14 1546 &ndash October 24 1601) was a Danish nobleman In 1610, Galileo Galilei became the first person known to point a telescope towards the sky. Galileo Galilei (15 February 1564 &ndash 8 January 1642 was a Tuscan ( Italian) Physicist, Mathematician, Astronomer, and Philosopher A telescope is an instrument designed for the observation of remote objects and the collection of Electromagnetic radiation. He immediately discovered the moons of Jupiter and the phases of Venus, among other things. The Galilean moons are the four moons of Jupiter discovered by Galileo Galilei. Planetary phase is the term used to describe the appearance of the illuminated section of a Planet. The VENUS ( V ictoria E xperimental N etwork U nder the S ea project is a cabled sea floor observatory operated by the University

Meteor showers are better observed by naked eye than with binoculars—the Perseids (10–12 August) or the December Geminids. The Perseids (ˈpɝsiːɨdz pûr'sē-ĭdz is a prolific Meteor shower associated with the Comet Swift-Tuttle. The Geminids are a Meteor shower caused by an object named 3200 Phaethon, which is thought to be an extinct Comet. Some 100 satellites per night, the International Space Station or the Milky Way are other popular visible objects. This article is about artificial satellites For natural satellites also known as moons see Natural satellite. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply

Space, geodesy, and navigation

Many other things can be estimated without an instrument. Geodesy (dʒiːˈɒdɪsi also called geodetics, a branch of Earth sciences, is the scientific discipline that deals Navigation is the process of reading and controlling the movement of a craft or vehicle from one place to another If an arm is stretched the span of the hand corresponds to an angle of 18 to 20°. The distance of a person, just covered up by the outstretched thumb, is about 600 meters. The vertical can be estimated to about 2° and, in the northern hemisphere, the Pole Star and a protractor gives the observer's geographic latitude, up to 1 degree. A pole star is a visible star especially a prominent one that is approximately aligned with the Earth 's Axis of rotation; that is a star whose apparent position Latitude, usually denoted symbolically by the Greek letter phi ( Φ) gives the location of a place on Earth (or other planetary body north or south of the

The Babylonians, Mayans and ancient Egyptians measured all the basics of their respective time and calendar systems by naked eye:

• the length of a year and a month to ±0. Babylonia was an Amorite state in lower Mesopotamia (modern southern Iraq) with Babylon as its capital The Maya civilization is a Mesoamerican Civilization, noted for the only known fully developed written language of the Pre-Columbian Americas Ancient Egypt was an Ancient Civilization in eastern North Africa, concentrated along the lower reaches of the Nile River in what is now For other uses see Time (disambiguation Time is a component of a measuring system used to sequence events to compare the durations of The word Calendar consist of two words 1 Cal ( in Pashto means Year in Hindi and Persian is Sal- also means Year A year (from Old English gēr) is the time between two recurrences of an event related to the Orbit of the Earth around the Sun The month is a unit of Time, used with Calendars which is approximately as long as some natural period related to the motion of the Moon; 1 hour or to better than 1 minute (0. 001%)
• the 24 hours of a day, and the equinoxes
• the periods of the Planets—by Mayan astronomers within 5 to 10 minutes for Venus and Mars. An equinox is the event of the Sun passing over the Earth's equator in its annual cycle A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is

In a similar manner star occultations by the moon can be observed. In Shia Islam The Occultation is a term used to designate the hidden state of the Imam of the Time. By using a digital clock one gets around 0. Circadian Locomotor Output Cycles Kaput, or Clock is a gene which encodes proteins regulating Circadian rhythm. 2 s —which represents only 200 meters at the moon's distance of 385,000 km.

Small objects and maps

Observing a nearby small object without a magnifying glass or a microscope, the usual distance is 20–25 cm. magnifying glass (called a hand lens in laboratory contexts is a convex lens which is used to produce a magnified Image of an object A microscope ( Greek: ( micron) = small + ( skopein) = to look or see is an instrument for viewing objects that are At this close range, 0. 05 mm can be seen clearly. The accuracy of a measurement depends on the experience (0. 1 to 0. 3 mm). The latter figure is the usual position accuracy of faint details in maps, and also of technical plans.

Environmental and light pollution

If the Milky Way is visible, this is an indicator for a clean atmosphere. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five If we look both at the zenith and toward the horizon, the "blue quality" will degrade depending on the air pollution and dust. The horizon ( Ancient Greek ὁ ὁρίζων, /ho horídzôn/ from ὁρίζειν, "to limit" is the apparent line that separates The star twinkling is a measure for the air turbulences — e. In Fluid dynamics, turbulence or turbulent flow is a fluid regime characterized by chaotic Stochastic property changes g. in meteorology and for the "seeing" of astronomy. Meteorology (from Greek grc μετέωρος metéōros, "high in the sky" and grc -λογία -logia) is the Interdisciplinary Astronomical seeing refers to the blurring and twinkling of astronomical objects such as stars caused by Turbulence in the Earth's atmosphere

Light pollution is a significant problem for amateur astronomers but becomes less late at night when many lights are shut off. Light pollution, also known as photopollution or luminous pollution, is excess or obtrusive Light created mainly by Humans Among other effects Air dust can be seen even far away of a city by its "light dome". In winter the snow cover in the city can be estimated without going there.

Literature

• Adobe Comp. : ”Photoshop”, program handbook, versions 5/6, Adobe 2002.
• Davidson, N. : Sky Phenomena: A Guide to Naked Eye Observation of the Heavens. FlorisBooks (208p), ISBN 0-86315-168-X, Edinburgh 1993.
• Gerstbach G. : Auge und Sehen — der lange Weg zu digitalem Erkennen. Astro Journal Sternenbote, 20p. The Sternenbote is a monthly Astronomy Journal, edited by the Austrian astronomical Society (Astroverein in Vienna. , Vol. 2000/8, Vienna 2000.
• Kahmen H. (Ed. ): Geodesy for Geotechnical and Structural Engineering. Proceedings, Eisenstadt 1999.

External links

• Naked Eye Observing in Astronomy
• Naked-Eye Stargazing: Learning the Sky and its constellations
• Naked Eye Navigation, Polynesia Voyages