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57-460: The night sky refers to the sky as it is seen at night. Night sky (or skies ) may also refer to: Night sky Natural light sources in a night sky include moonlight , starlight , and airglow , depending on location and timing. Aurorae light up the skies above the polar circles . Occasionally, a large coronal mass ejection from the Sun or simply high levels of solar wind may extend

114-425: A celestial object in a telescope equipped with a DSC computer, one does not need to look up the specific RA and Dec coordinates in a book or other resource, and then adjust the telescope to those numerical readings. Rather, the object is chosen from the electronic database, which causes distance values and arrow markers to appear in the display that indicate the distance and direction to move the telescope. The telescope

171-481: A decade. They tend to be visible only shortly before sunrise or after sunset because those are the times they are close enough to the Sun to show a tail. Clouds obscure the view of other objects in the sky, though varying thicknesses of cloud cover have differing effects. A very thin cirrus cloud in front of the moon might produce a rainbow-colored ring around the moon . Stars and planets are too small or dim to take on this effect and are instead only dimmed (often to

228-558: A distance from other objects because their navigation lights blink. Beside the Solar System objects changing in the course of them and Earth orbiting and changing orbits over time around the Sun and in the case of the Moon around Earth, appearing over time smaller by expanding its orbit, the night sky also changes over the course of the years with stars having a proper motion and changing brightness because of being variable stars , by

285-480: A dome. Orion is among the most prominent and recognizable constellations. The Big Dipper (which has a wide variety of other names) is helpful for navigation in the northern hemisphere because it points to Polaris , the north star. The pole stars are special because they are approximately in line with the Earth's axis of rotation so they appear to stay in one place while the other stars rotate around them through

342-472: A few specific techniques. Star hopping is a method often used by amateur astronomers with low-tech equipment such as binoculars or a manually driven telescope. It involves the use of maps (or memory) to locate known landmark stars, and "hopping" between them, often with the aid of a finderscope . Because of its simplicity, star hopping is a very common method for finding objects that are close to naked-eye stars. More advanced methods of locating objects in

399-422: A small local society located in dark countryside may focus on practical observing and star parties , whereas a large one based in a major city might have numerous members but be limited by light pollution and thus hold regular indoor meetings with guest speakers instead. Major national or international societies generally publish their own academic journal or newsletter, and some hold large multi-day meetings akin to

456-846: A telescope a great distance away in a dark location. The observer can image through the telescope using CCD cameras. The digital data collected by the telescope is then transmitted and displayed to the user by means of the Internet. An example of a digital remote telescope operation for public use via the Internet is the Bareket observatory , and there are telescope farms in New Mexico, Australia and Atacama in Chile. Amateur astronomers engage in many imaging techniques including film, DSLR , LRGB , and CCD astrophotography . Because CCD imagers are linear, image processing may be used to subtract away

513-424: Is a way for the hobby lovers to share their new sightings and experiences. The popularity of imaging among amateurs has led to large numbers of web sites being written by individuals about their images and equipment. Much of the social interaction of amateur astronomy occurs on mailing lists or discussion groups. Discussion group servers host numerous astronomy lists. A great deal of the commerce of amateur astronomy,

570-451: Is about the size of a thumbnail at arm's length, and is readily identified. Over 29.53 days on average, the moon goes through a full cycle of lunar phases . People can generally identify phases within a few days by looking at the Moon. Unlike stars and most planets, the light reflected from the Moon is bright enough to be seen during the day. Some of the most spectacular moons come during the full moon phase near sunset or sunrise. The Moon on

627-446: Is brighter than the stars and often the only "star" visible near sunrise or sunset, depending on its location in its orbit. Because of its brightness, Venus can sometimes be seen after sunrise. Mercury , Mars , Jupiter and Saturn are also visible to the naked eye in the night sky. The Moon appears as a grey disc in the sky with cratering visible to the naked eye. It spans, depending on its exact location, 29–33 arcminutes – which

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684-469: Is moved until the two angular distance values reach zero, indicating that the telescope is properly aligned. When both the RA and Dec axes are thus "zeroed out", the object should be in the eyepiece. Many DSCs, like go-to systems, can also work in conjunction with laptop sky programs. Computerized systems provide the further advantage of computing coordinate precession. Traditional printed sources are subtitled by

741-409: Is one such example. Amateur astronomers use a range of instruments to study the sky, depending on a combination of their interests and resources. Methods include simply looking at the night sky with the naked eye, using binoculars, and using a variety of optical telescopes of varying power and quality, as well as additional sophisticated equipment, such as cameras, to study light from the sky in both

798-496: Is possible for amateurs to see them. There are a large number of amateur astronomical societies around the world, that serve as a meeting point for those interested in amateur astronomy. Members range from active observers with their own equipment to "armchair astronomers" who are simply interested in the topic. Societies range widely in their goals and activities, which may depend on a variety of factors such as geographic spread, local circumstances, size, and membership. For example,

855-624: Is searching for overlooked phenomena (e.g., Kreutz Sungrazers ) in the vast libraries of digital images and other data captured by Earth and space based observatories, much of which is available over the Internet. In the past and present, amateur astronomers have played a major role in discovering new comets . Recently however, funding of projects such as the Lincoln Near-Earth Asteroid Research and Near Earth Asteroid Tracking projects has meant that most comets are now discovered by automated systems long before it

912-619: Is sometimes promoted as one of the few remaining sciences for which amateurs can still contribute useful data. To recognize this, the Astronomical Society of the Pacific annually gives Amateur Achievement Awards for significant contributions to astronomy by amateurs. The majority of scientific contributions by amateur astronomers are in the area of data collection. In particular, this applies where large numbers of amateur astronomers with small telescopes are more effective than

969-460: The epoch year , which refers to the positions of celestial objects at a given time to the nearest year (e.g., J2005, J2007). Most such printed sources have been updated for intervals of only about every fifty years (e.g., J1900, J1950, J2000). Computerized sources, on the other hand, are able to calculate the right ascension and declination of the "epoch of date" to the exact instant of observation. GOTO telescopes have become more popular since

1026-517: The International Space Station (ISS) and Iridium Satellites . Meteors streak across the sky infrequently. During a meteor shower , they may average one a minute at irregular intervals, but otherwise their appearance is a random surprise. The occasional meteor will make a bright, fleeting streak across the sky, and they can be very bright in comparison to the night sky. Aircraft are also visible at night, distinguishable at

1083-516: The backscatter of sunlight by interplanetary dust . Shortly after sunset and before sunrise, artificial satellites often look like stars – similar in brightness and size – but move relatively quickly. Those that fly in low Earth orbit cross the sky in a couple of minutes. Some satellites, including space debris , appear to blink or have a periodic fluctuation in brightness because they are rotating. Satellite flares can appear brighter than Venus, with notable examples including

1140-425: The rod cells without triggering the cone cells . If it is particularly dark and a particularly faint celestial object is of interest, averted vision may be helpful. The stars of the night sky cannot be counted unaided because they are so numerous and there is no way to track which have been counted and which have not. Further complicating the count, fainter stars may appear and disappear depending on exactly where

1197-541: The sky using the unaided eye , binoculars , or telescopes . Even though scientific research may not be their primary goal, some amateur astronomers make contributions in doing citizen science , such as by monitoring variable stars , double stars , sunspots , or occultations of stars by the Moon or asteroids , or by discovering transient astronomical events , such as comets , galactic novae or supernovae in other galaxies . Amateur astronomers do not use

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1254-468: The 1980s as technology has improved and prices have been reduced. With these computer-driven telescopes, the user typically enters the name of the item of interest and the mechanics of the telescope point the telescope towards that item automatically. They have several notable advantages for amateur astronomers intent on research. For example, GOTO telescopes tend to be faster for locating items of interest than star hopping, allowing more time for studying of

1311-456: The advent of artificial light sources, however, light pollution has been a growing problem for viewing the night sky. Optical filters and modifications to light fixtures can help to alleviate this problem, but for optimal views, both professional and amateur astronomers seek locations far from urban skyglow . The fact that the sky is not completely dark at night, even in the absence of moonlight and city lights, can be easily observed, since if

1368-415: The alignment process of telescopes. Setting circles are angular measurement scales that can be placed on the two main rotation axes of some telescopes. Since the widespread adoption of digital setting circles, any classical engraved setting circle is now specifically identified as an "analog setting circle" (ASC). By knowing the coordinates of an object (usually given in equatorial coordinates ),

1425-727: The beginning of the twentieth century, professional astronomy has become an activity clearly distinguished from amateur astronomy and associated activities. Amateur astronomers typically view the sky at night, when most celestial objects and astronomical events are visible, but others observe during the daytime by viewing the Sun and solar eclipses . Some just look at the sky using nothing more than their eyes or binoculars, but more dedicated amateurs often use portable telescopes or telescopes situated in their private or club observatories . Amateurs also join amateur astronomical societies , which can advise, educate or guide them towards ways of finding and observing celestial objects. They also promote

1482-426: The belief that relationships between heavenly bodies influence or explain events on Earth. The scientific study of objects in the night sky takes place in the context of observational astronomy . Visibility of celestial objects in the night sky is affected by light pollution . The presence of the Moon in the night sky has historically hindered astronomical observation by increasing the amount of sky brightness . With

1539-531: The buying and selling of equipment, occurs online. Many amateurs use online tools to plan their nightly observing sessions, using tools such as the Clear Sky Chart . While a number of interesting celestial objects are readily identified by the naked eye, sometimes with the aid of a star chart, many others are so faint or inconspicuous that technical means are necessary to locate them. Although many methods are used in amateur astronomy, most are variations of

1596-452: The course of a night (or a year). Planets , named for the Greek word for 'wanderer', process through the starfield a little each day, executing loops with time scales dependent on the length of the planet's year or orbital period around the Sun. Planets, to the naked eye, appear as points of light in the sky with variable brightness. Planets shine due to sunlight reflecting or scattering from

1653-504: The dark adaptation. Star charts are produced to aid stargazers in identifying constellations and other celestial objects. Constellations are prominent because their stars tend to be brighter than other nearby stars in the sky. Different cultures have created different groupings of constellations based on differing interpretations of the more-or-less random patterns of dots in the sky. Constellations were identified without regard to distance to each star, but instead as if they were all dots on

1710-605: The distance to them getting larger or other celestial events like supernovas . Over a timescale of tens of billions of years the night sky in the Local Group will significantly change when the coalescence of the Andromeda Galaxy and the Milky Way merge into a single elliptical galaxy. Stargazing Amateur astronomy is a hobby where participants enjoy observing or imaging celestial objects in

1767-438: The effects of light pollution, which has increased the popularity of astrophotography in urban areas. Narrowband filters may also be used to minimize light pollution. Scientific research is most often not the main goal for many amateur astronomers, unlike professional astronomers. Work of scientific merit is possible, however, and many amateurs successfully contribute to the knowledge base of professional astronomers. Astronomy

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1824-403: The entire night sky. A range of astronomy software is also available and used by amateur astronomers, including software that generates maps of the sky, software to assist with astrophotography, observation scheduling software, and software to perform various calculations pertaining to astronomical phenomena. Amateur astronomers often like to keep records of their observations, which usually takes

1881-425: The field of astronomy as their primary source of income or support, and usually have no professional degree in astrophysics or advanced academic training in the subject. Most amateurs are hobbyists, while others have a high degree of experience in astronomy and may often assist and work alongside professional astronomers. Many astronomers have studied the sky throughout history in an amateur framework; however, since

1938-454: The form of an observing log. Observing logs typically record details about which objects were observed and when, as well as describing the details that were seen. Sketching is sometimes used within logs, and photographic records of observations have also been used in recent times. The information gathered is used to help studies and interactions between amateur astronomers in yearly gatherings. Although not professional information or credible, it

1995-418: The hobby of amateur astronomy. Although specialized and experienced amateur astronomers tend to acquire more specialized and more powerful equipment over time, relatively simple equipment is often preferred for certain tasks. Binoculars, for instance, although generally of lower power than the majority of telescopes, also tend to provide a wider field of view , which is preferable for looking at some objects in

2052-403: The horizon benefits from the Moon illusion which makes it appear larger. The Sun's light reflected from the Moon traveling through the atmosphere also appears to color the Moon orange and/or red. Comets come to the night sky only rarely. Comets are illuminated by the Sun, and their tails extend away from the Sun. A comet with a visible tail is quite unusual – a great comet appears about once

2109-469: The night sky. Recent models of iPhones have introduced a "night mode " option when taking pictures as well, that allows you to increase exposure, which is a period of time the picture is being taken for. This optimizes focus on light in the frame which is why it is used primarily at night. Amateur astronomers also use star charts that, depending on experience and intentions, may range from simple planispheres through to star atlases with detailed charts of

2166-406: The object. GOTO also allows manufacturers to add equatorial tracking to mechanically simpler alt-azimuth telescope mounts, allowing them to produce an overall less expensive product. GOTO telescopes usually have to be calibrated using alignment stars to provide accurate tracking and positioning. However, several telescope manufacturers have recently developed telescope systems that are calibrated with

2223-466: The observer is looking. The result is an impression of an extraordinarily vast star field. Because stargazing is best done from a dark place away from city lights, dark adaptation is important to achieve and maintain. It takes several minutes for eyes to adjust to the darkness necessary for seeing the most stars, and surroundings on the ground are hard to discern. A red flashlight can be used to illuminate star charts and telescope parts without undoing

2280-418: The period from −12° to −18°. When the Sun drops more than 18° below the horizon, the sky generally attains its minimum brightness. Several sources can be identified as the source of the intrinsic brightness of the sky, namely airglow , indirect scattering of sunlight, scattering of starlight, and artificial light pollution . Depending on local sky cloud cover, pollution, humidity, and light pollution levels,

2337-514: The phenomenon toward the Equator . The night sky and studies of it have a historical place in both ancient and modern cultures. In the past, for instance, farmers have used the status of the night sky as a calendar to determine when to plant crops. Many cultures have drawn constellations between stars in the sky, using them in association with legends and mythology about their deities . The history of astrology has generally been based on

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2394-403: The planets' surface or atmosphere. Thus, the relative Sun-planet-Earth positions determine the planet's brightness. With a telescope or good binoculars, the planets appear as discs demonstrating finite size, and it is possible to observe orbiting moons which cast shadows onto the host planet's surface. Venus is the most prominent planet, often called the "morning star" or "evening star" because it

2451-459: The point of invisibility). Thicker cloud cover obscures celestial objects entirely, making the sky black or reflecting city lights back down. Clouds are often close enough to afford some depth perception, though they are hard to see without moonlight or light pollution. On clear dark nights in unpolluted areas, when the Moon appears thin or below the horizon, the Milky Way, a band of what looks like white dust, can be seen. The Magellanic Clouds of

2508-646: The relatively small number of large telescopes that are available to professional astronomers. Several organizations, such as the American Association of Variable Star Observers and the British Astronomical Association , exist to help coordinate these contributions. Amateur astronomers often contribute toward activities such as monitoring the changes in brightness of variable stars and supernovae , helping to track asteroids , and observing occultations to determine both

2565-590: The science of astronomy among the general public. Collectively, amateur astronomers observe a variety of celestial objects and phenomena. Common targets of amateur astronomers include the Sun , the Moon , planets , stars , comets , meteor showers , and a variety of deep sky objects such as star clusters , galaxies , and nebulae . Many amateurs like to specialise in observing particular objects, types of objects, or types of events which interest them. One branch of amateur astronomy, amateur astrophotography , involves

2622-420: The shape of asteroids and the shape of the terrain on the apparent edge of the Moon as seen from Earth. With more advanced equipment, but still cheap in comparison to professional setups, amateur astronomers can measure the light spectrum emitted from astronomical objects, which can yield high-quality scientific data if the measurements are performed with due care. A relatively recent role for amateur astronomers

2679-436: The situation is more complicated and a further differentiation is required. Twilight is divided in three segments according to how far the Sun is below the horizon in segments of 6°. After sunset the civil twilight sets in, and ends when the Sun drops more than 6° below the horizon. This is followed by the nautical twilight , when the Sun reaches heights of −6° and −12°, after which comes the astronomical twilight defined as

2736-474: The sky include telescope mounts with setting circles , which allow pointing to targets in the sky using celestial coordinates , and GOTO telescopes , which are fully automated telescopes that are capable of locating objects on demand (having first been calibrated). The advent of mobile applications for use in smartphones has led to the creation of many dedicated apps. These apps allow any user to easily locate celestial objects of interest by simply pointing

2793-419: The sky were absolutely dark, one would not be able to see the silhouette of an object against the sky. The intensity of the sky brightness varies greatly over the day and the primary cause differs as well. During daytime when the Sun is above the horizon direct scattering of sunlight ( Rayleigh scattering ) is the overwhelmingly dominant source of light. In twilight, the period of time between sunset and sunrise,

2850-419: The smartphone device in that direction in the sky. These apps make use of the inbuilt hardware in the phone, such as GPS location and gyroscope . Useful information about the pointed object like celestial coordinates, the name of the object, its constellation, etc. are provided for a quick reference. Some paid versions give more information. These apps are gradually getting into regular use during observing, for

2907-425: The southern sky are easily mistaken to be Earth-based clouds (hence the name) but are in fact collections of stars found outside the Milky Way known as dwarf galaxies . Zodiacal light is a glow that appears near the points where the Sun rises and sets, and is caused by sunlight interacting with interplanetary dust . Gegenschein is a faint bright spot in the night sky centered at the antisolar point , caused by

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2964-515: The stars visible to the unaided naked eye appear as hundreds, thousands or tens of thousands of white pinpoints of light in an otherwise near black sky together with some faint nebulae or clouds of light. In ancient times the stars were often assumed to be equidistant on a dome above the Earth because they are much too far away for stereopsis to offer any depth cues. Visible stars range in color from blue (hot) to red (cold), but with such small points of faint light, most look white because they stimulate

3021-441: The taking of photos of the night sky. Astrophotography has become more popular with the introduction of far easier to use equipment including, digital cameras, DSLR cameras and relatively sophisticated purpose built high quality CCD cameras and CMOS cameras . Most amateur astronomers work at visible wavelengths , but a small minority experiment with wavelengths outside the visible spectrum . An early pioneer of radio astronomy

3078-659: The telescope user can use the setting circle to align (i.e., point) the telescope in the appropriate direction before looking through its eyepiece . A computerized setting circle is called a "digital setting circle" (DSC). Although digital setting circles can be used to display a telescope's RA and Dec coordinates, they are not simply a digital read-out of what can be seen on the telescope's analog setting circles. As with go-to telescopes, digital setting circle computers (commercial names include Argo Navis, Sky Commander, and NGC Max) contain databases of tens of thousands of celestial objects and projections of planet positions. To find

3135-511: The use of built-in GPS, decreasing the time it takes to set up a telescope at the start of an observing session. With the development of fast internet in the last part of the 20th century along with advances in computer controlled telescope mounts and CCD cameras, "remote telescope" astronomy is now a viable means for amateur astronomers not aligned with major telescope facilities to partake in research and deep sky imaging. This enables anyone to control

3192-454: The visual and non-visual parts of the spectrum. To further improve studying the visual and non-visual part of the spectrum, amateur astronomers go to rural areas to get away from light pollution . Commercial telescopes are available, new and used, but it is also common for amateur astronomers to build (or commission the building of) their own custom telescopes. Some people even focus on amateur telescope making as their primary interest within

3249-570: Was Grote Reber , an amateur astronomer who constructed the first purpose-built radio telescope in the late 1930s to follow up on the discovery of radio wavelength emissions from space by Karl Jansky . Non-visual amateur astronomy includes the use of infrared filters on conventional telescopes, and also the use of radio telescopes . Some amateur astronomers use home-made radio telescopes, while others use radio telescopes that were originally built for astronomical research but have since been made available for use by amateurs. The One-Mile Telescope

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