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103-612: The La Silla telescopes and instruments are located 150 km northeast of La Serena , on the outskirts of the Atacama Desert , one of the driest and most remote areas in the world. Like other observatories in this region, La Silla is far from sources of light pollution and, like the Paranal Observatory —home to the Very Large Telescope —it has some of the darkest night skies on Earth. Following

206-449: A ( ρ ) {\displaystyle D_{\phi _{a}}\left({\mathbf {\rho } }\right)} is the atmospherically induced variance between the phase at two parts of the wavefront separated by a distance ρ {\displaystyle {\boldsymbol {\rho }}} in the aperture plane, and ⟨ ⋅ ⟩ {\displaystyle \langle \cdot \rangle } represents

309-550: A ( r ) {\displaystyle \phi _{a}\left(\mathbf {r} \right)} describe the effect of the Earth's atmosphere, and the timescales for any changes in these functions will be set by the speed of refractive index fluctuations in the atmosphere. A description of the nature of the wavefront perturbations introduced by the atmosphere is provided by the Kolmogorov model developed by Tatarski, based partly on

412-413: A ( r ) {\displaystyle \phi _{a}\left(\mathbf {r} \right)} , but any amplitude fluctuations are only brought about as a second-order effect while the perturbed wavefronts propagate from the perturbing atmospheric layer to the telescope. For all reasonable models of the Earth's atmosphere at optical and infrared wavelengths the instantaneous imaging performance is dominated by

515-480: A ( r ) e i ϕ a ( r ) ) ψ 0 ( r ) {\displaystyle \psi _{p}\left(\mathbf {r} \right)=\left(\chi _{a}\left(\mathbf {r} \right)e^{i\phi _{a}\left(\mathbf {r} \right)}\right)\psi _{0}\left(\mathbf {r} \right)} where χ a ( r ) {\displaystyle \chi _{a}\left(\mathbf {r} \right)} represents

618-469: A ( r ) {\displaystyle \phi _{a}(\mathbf {r} )} is the optical phase error introduced by atmospheric turbulence, R (k) is a two-dimensional square array of independent random complex numbers which have a Gaussian distribution about zero and white noise spectrum, K (k) is the (real) Fourier amplitude expected from the Kolmogorov (or Von Karman) spectrum, Re[] represents taking

721-419: A ( r ) = Re ⁡ [ FT [ ( R ( k ) ⊗ I ( k ) ) K ( k ) ] ] {\displaystyle \phi _{a}(\mathbf {r} )=\operatorname {Re} [{\mbox{FT}}[(R(\mathbf {k} )\otimes I(\mathbf {k} ))K(\mathbf {k} )]]} where I ( k ) is a two-dimensional array which represents the spectrum of intermittency, with

824-778: A coastal zone, the minimums and maximums are moderated by the maritime influence and the temperature of the cold Humboldt Current . Winter (specifically from May to August) is the rainy season, with a total rainfall of approximately 100 mm (3.94 in) annually in a normal year, notable exceptions being the year 1997 which experienced a total rainfall in the city near 200 mm (7.87 in), 1880 with 366 millimetres (14.41 in) and 1888 when as much as 417 millimetres (16.42 in) fell including 239 millimetres (9.41 in) in August. The driest year has been 1979 with only 4.5 millimetres (0.18 in), whilst recent years, as in central Chile and Zona Sur , have tended to be drier than

927-769: A commonly used definition for r 0 {\displaystyle r_{0}} , a parameter frequently used to describe the atmospheric conditions at astronomical observatories. r 0 {\displaystyle r_{0}} can be determined from a measured C N profile (described below) as follows: r 0 = ( 16.7 λ − 2 ( cos ⁡ γ ) − 1 ∫ 0 ∞ C N 2 ( h ) d h ) − 3 / 5 {\displaystyle r_{0}=\left(16.7\lambda ^{-2}(\cos \gamma )^{-1}\int _{0}^{\infty }C_{N}^{2}(h)dh\right)^{-3/5}} where

1030-693: A communal population of roughly 200,000, and was one of the fastest-growing areas of Chile. The city is an important tourist destination for Chileans and Argentines, especially during the summer, where people go to visit the beaches. It is the headquarters of the University of La Serena and also is home to the Roman Catholic Archdiocese of La Serena , one of five Catholic Archdioceses of the Catholic Church in Chile. The sector

1133-599: A crucial role in linking gamma-ray bursts —the most energetic explosions in the Universe since the Big Bang—with the explosions of massive stars. Since 1987, the ESO La Silla Observatory has also played an important role in the study and follow-up of the nearest recent supernova, SN 1987A . Hundreds of rock engravings, also called petroglyphs , can be found all around La Silla. These are attributed to

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1236-407: A filled disc called the "seeing disc". The diameter of the seeing disk, most often defined as the full width at half maximum (FWHM), is a measure of the astronomical seeing conditions. It follows from this definition that seeing is always a variable quantity, different from place to place, from night to night, and even variable on a scale of minutes. Astronomers often talk about "good" nights with

1339-636: A first light in 1980. It was retired in 1998, when the Euler Telescope was commissioned. The Swiss T70 was a Cassegrain reflector design mounted on an Equatorial fork mount. It was equipped with a P7 Photometer, and replaced the Swiss 0.4-metre telescope , which was in use from November 1975 until March 1980. As with the Euler Telescope, the Swiss T70 and 0.4-metre telescopes were operated by

1442-475: A low average seeing disc diameter, and "bad" nights where the seeing diameter was so high that all observations were worthless. The FWHM of the seeing disc (or just "seeing") is usually measured in arcseconds , abbreviated with the symbol (″). A 1.0″ seeing is a good one for average astronomical sites. The seeing of an urban environment is usually much worse. Good seeing nights tend to be clear, cold nights without wind gusts. Warm air rises ( convection ), degrading

1545-503: A new secondary mirror that has kept the telescope in its place as one of the most efficient and productive engines of astronomical research. The telescope hosts HARPS , the High Accuracy Radial velocity Planet Searcher, the world's foremost exoplanet hunter. HARPS is a spectrograph with unrivalled precision and is the most successful finder of low-mass exoplanets to date. Since 2022, the 3.6 m telescope has also hosted NIRPS,

1648-439: A surface area of 1,892.8 km (731 sq mi). The city is located on ocean terraces , which are clearly noticeable from the coastal area, through downtown to the eastern sector Vicuña way. The rest of the urban area is based on several small hills, valleys and plains. The city is commonly divided into various sectors. In the north is the airline sector, subdivided into two sub-sectors called High and Low Company. Nearby

1751-409: A telescope. The perturbed wavefront ψ p {\displaystyle \psi _{p}} may be related at any given instant to the original planar wavefront ψ 0 ( r ) {\displaystyle \psi _{0}\left(\mathbf {r} \right)} in the following way: ψ p ( r ) = ( χ

1854-400: A total area of 1,892 square kilometres (731 sq mi). A few of the major city sectors are: El Centro ("downtown"), Peñuelas (actually a suburb between La Serena and Coquimbo ), San Joaquín (neighborhood on a hill overlooking the ocean), La Florida, Las Compañías ("the companies"), Cerro Grande ("big hill"), La Antena and the new El Milagro ("the miracle") development. The commune spans

1957-694: A twin brother located at the Calar Alto Observatory in southern Spain. La Silla also hosts several national and project telescopes not operated by ESO. Among them are the Swiss Euler Telescope, the Danish National Telescope and the REM, TRAPPIST and TAROT telescopes. The following telescopes have now been decommissioned: The Swiss T70 telescope was a 70 cm aperture telescope for photometry that had

2060-577: A wide variety of schools, lyceums and universities, concentrating great part of the academical offer in the region. Among primary and secondary education, La Serena hosts public, subsidized (owned by the State, managed by privates), and privates schools (La Serena currently holds the entirety of private schools within the Greater La Serena area). Among the universities present in La Serena are

2163-410: Is 10–20 cm at visible wavelengths under the best conditions) and this limits the resolution of telescopes to be about the same as given by a space-based 10–20 cm telescope. The distortion changes at a high rate, typically more frequently than 100 times a second. In a typical astronomical image of a star with an exposure time of seconds or even minutes, the different distortions average out as

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2266-718: Is San Pedro Creek. To the south are the areas of La Pampa, San Joaquin and the El Milagro. To the east are the sectors of La Antena, Juan XXIII, La Florida, Colina El Pino and the University District. Finally, to the west is the area of Avenida del Mar. Areas surrounding the city are mainly areas for growing vegetables, and there are a large number of plantations for the cultivation of chirimoyas , avocados and oranges, in addition to where vegetation has an average with some areas found mainly eucalyptus forests. These areas are normally conducive to wildfires sparked during

2369-413: Is a commonly used measurement of the astronomical seeing at observatories. At visible wavelengths, r 0 {\displaystyle r_{0}} varies from 20 cm at the best locations to 5 cm at typical sea-level sites. In reality, the pattern of blobs ( speckles ) in the images changes very rapidly, so that long-exposure photographs would just show a single large blurred blob in

2472-492: Is an organ donated by the philanthropist Juana Ross de Edwards. The belfry dates back from the 20th century. The town has retained its historic architecture and this, along with a selection of beaches (known as Avenida del Mar , "Sea Avenue"), has caused the city to become a significant tourist destination, attracting many foreigners (most of them Argentines from San Juan and Mendoza provinces) during January, and later Santiago residents fleeing February heat. The beaches of

2575-549: Is assumed to occur on slow timescales, then the timescale t 0 is simply proportional to r 0 divided by the mean wind speed. The refractive index fluctuations caused by Gaussian random turbulence can be simulated using the following algorithm: ϕ a ( r ) = Re [ FT [ R ( k ) K ( k ) ] ] {\displaystyle \phi _{a}(\mathbf {r} )={\mbox{Re}}[{\mbox{FT}}[R(\mathbf {k} )K(\mathbf {k} )]]} where ϕ

2678-533: Is currently located where the city was inhabited by the pre-Hispanic village called Viluma or Vilumanque ( Mapudungún Snakes and condors). La Serena was founded on the orders of the Spaniard Pedro de Valdivia in order to provide a sea link to maintain permanent contact between Santiago and Lima in the Viceroyalty of Peru . For this he would need a place for his troops to rest and eat. The village

2781-592: Is on indefinite loan to ESO from the Max Planck Society (German: Max Planck Gesellschaft or MPG). Telescope time is shared between MPG and ESO observing programmes, while the operation and maintenance of the telescope are ESO's responsibility. However, due to a new agreement between the Max Planck Institute for Astronomy (MPIA) and ESO, the instrument is operated by MPG until the end of September 2016. The telescope hosts three instruments:

2884-439: Is one of the famous and works awesome with swells. The best Enduro mountainbike spot is Cerro Grande just behind La Serena with several trails only for advanced to expert riders. La Serena relies on diverse means of transport to connect downtown with peripheral neighborhoods and Coquimbo , such as collective taxis , taxis and tour buses. In the past the city was the principal railway center for passenger transport to travel to

2987-462: Is the Dirac delta function . A more thorough description of the astronomical seeing at an observatory is given by producing a profile of the turbulence strength as a function of altitude, called a C n 2 {\displaystyle C_{n}^{2}} profile. C n 2 {\displaystyle C_{n}^{2}} profiles are generally performed when deciding on

3090-401: Is the complex field at position r {\displaystyle \mathbf {r} } and time t {\displaystyle t} , with real and imaginary parts corresponding to the electric and magnetic field components, ϕ u {\displaystyle \phi _{u}} represents a phase offset, ν {\displaystyle \nu } is

3193-693: Is treated as an oscillation in a field ψ {\displaystyle \psi } . For monochromatic plane waves arriving from a distant point source with wave-vector k {\displaystyle \mathbf {k} } : ψ 0 ( r , t ) = A u e i ( ϕ u + 2 π ν t + k ⋅ r ) {\displaystyle \psi _{0}\left(\mathbf {r} ,t\right)=A_{u}e^{i\left(\phi _{u}+2\pi \nu t+\mathbf {k} \cdot \mathbf {r} \right)}} where ψ 0 {\displaystyle \psi _{0}}

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3296-553: The C n 2 {\displaystyle C_{n}^{2}} profile. Some are empirical fits from measured data and others attempt to incorporate elements of theory. One common model for continental land masses is known as Hufnagel-Valley after two workers in this subject. The first answer to this problem was speckle imaging , which allowed bright objects with simple morphology to be observed with diffraction-limited angular resolution. Later came space telescopes , such as NASA 's Hubble Space Telescope , working outside

3399-605: The Avenida Del Mar are some of the most crowded in La Serena, which run from the El Faro Monumental in the south to Peñuelas's beach in neighboring Coquimbo, an extension of 6 km (4 mi). However, the beaches of La Serena have very rough water and are not suitable for swimming. In comparison, beaches in Coquimbo, such as The Horseshoe, have very calm waters and clean sands. The twelve beaches along

3502-625: The Avenida del Mar are El Faro, Los Fuertes, Mansa, Blanca, La Barca, Cuatro Esquinas, La Marina, El Pescador, El Corsario, Hipocampo, Las Gaviotas, and Canto del Agua. All of them except the beacon are suitable for the swimming and aquatic and nautical sports. In recent years the La Serena Song Festival (created in 2004) has been gaining national importance, due to the high quality of the invited artists. A new international airport has also been improved. Real estate development along

3605-590: The Geneva Observatory . About 300 scientific papers based on observations taken at La Silla are published each year. The HARPS spectrograph has found a large number of low-mass extrasolar planets. It detected the planets within the Gliese 581 planetary system , which contains what may be the first known rocky planet in a habitable zone , outside the Solar System. Several telescopes at La Silla played

3708-678: The La Florida Airport to an area near Tongoy, Coquimbo, due to population growth close to the current airport with all the danger that this implies. The city has a football team called Club Deportes La Serena that plays in the second tier of the Chilean league of football. Their home games are played at the La Portada stadium, which has seating for approximately 18,000 spectators. Their biggest rivals are near-neighbors Coquimbo Unido . They are nicknamed "Los Papayeros", because of

3811-671: The University of La Serena , traditional university with its headquarters and four other campuses in the city; other institutions include the Universidad Central ( Central University ), Universidad Santo Tomás ( Saint Thomas University ), Universidad Tecnológica de Chile – INACAP ( Technological University of Chile ), and Universidad del Mar La Serena holds offices for the European Southern Observatory organisation (operator of La Silla Observatory ), AURA, Inc. (operator of Cerro Tololo , located in

3914-661: The Valle de Elqui , about 85 km east of La Serena, and Gemini observatories), and for the Carnegie Institution for Science (operator of Las Campanas Observatory ). It will also be the home of the base facility of the Vera C. Rubin Observatory . La Serena is twinned with: Astronomical seeing In astronomy , seeing is the degradation of the image of an astronomical object due to turbulence in

4017-515: The active optics give the excellent image quality of the NTT. The NTT has active instead of adaptive optics : it corrects the defects and deformation of the telescope and mirror, but does not correct the turbulence; it ensures that the optics is always in perfect shape. Together with the thermal control, it allows the NTT to reach the ambient seeing, but it does not improve it. The 2.2-metre telescope has been in operation at La Silla since early 1984, and

4120-408: The atmosphere of Earth that may become visible as blurring, twinkling or variable distortion . The origin of this effect is rapidly changing variations of the optical refractive index along the light path from the object to the detector. Seeing is a major limitation to the angular resolution in astronomical observations with telescopes that would otherwise be limited through diffraction by

4223-438: The strength of the phase fluctuations as it corresponds to the diameter of a circular telescope aperture at which atmospheric phase perturbations begin to seriously limit the image resolution. Typical r 0 {\displaystyle r_{0}} values for I band (900 nm wavelength) observations at good sites are 20–40 cm. r 0 {\displaystyle r_{0}} also corresponds to

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4326-549: The 1990s and in 2017 some vandalism was discovered. Another ESO site with archaeological testimonies in its vicinity is the ALMA site. La Serena, Chile La Serena ( Spanish pronunciation: [la seˈɾena] ) is a city and commune in northern Chile , capital of the Coquimbo Region . Founded in 1544, it is the country's second oldest city after the national capital, Santiago . As of 2012, it had

4429-576: The 1990s, many telescopes have developed adaptive optics systems that partially solve the seeing problem. The best systems so far built, such as SPHERE on the ESO VLT and GPI on the Gemini telescope, achieve a Strehl ratio of 90% at a wavelength of 2.2 micrometers, but only within a very small region of the sky at a time. A wider field of view can be obtained by using multiple deformable mirrors conjugated to several atmospheric heights and measuring

4532-408: The 1992 and 2002 censuses, making it one of the fastest-growing regions of the country. Had that growth continued, INE estimated the population would increase to 205,120 by 2008 and 244,070 by 2012, so the growth rate has dropped since then. In 2002 155,815 persons lived in the city proper, and La Serena was part of the country's fourth largest conurbation (pop. 300,000) with nearby Coquimbo , with

4635-422: The 300 to 700 CE El Molle culture . The El Molle culture have their origin as hunter-gatherers that developed a new way of life based on horticulture and village life. They are known for their pottery and body ornaments, such as necklaces and the tembetás . There are three types of petroglyph designs at La Silla: human and animal figures, abstract geometrical designs and purely ornamental ensembles. Beside

4738-604: The 67-million pixel Wide Field Imager with a field of view as large as the full Moon, which has taken many amazing images of celestial objects; GROND, the Gamma-Ray Burst Optical/Near-Infrared Detector, which chases the afterglows of the most powerful explosions in the Universe, known as gamma-ray bursts ; and the high-resolution spectrograph, FEROS, used to make detailed studies of stars. MPG's 2.2-metre telescope in La Silla also has

4841-466: The 7th electoral district, (together with La Higuera , Vicuña , Paihuano and Andacollo ). The commune is represented in the Senate by Sergio Gahona Salazar (UDI), Daniel Núñez Arancibia (PC) and Matías Walker Prieto (PDC) as part of the fourth senatorial constituency (Coquimbo Region). In the last decades, tourism has turned into one of the most important economic activities. The population doubles in

4944-606: The Cinchado, it was renamed La Silla ("the saddle" in Spanish) after its saddle-like shape. On October 30, 1964, the contracts were signed and an area of 627 square kilometres (242.1  sq mi ) was purchased the following year. During 1965, temporary facilities were erected with living quarters, a workshop and storage area. The dedication ceremony of the road to the summit took place in March 1966, two months after completion of

5047-515: The ESO 1-metre Schmidt Telescope, the 1.54-m Danish Telescope, the 1.2-m Leonhard Euler Telescope, the Rapid Eye Mount telescope, TRAPPIST and TAROT. These telescopes are not operated by ESO and hence do not fall under the responsibility of La Silla Science Operations. This 3.6 m Cassegrain telescope started operations in 1976 and has been constantly upgraded since, including the installation of

5150-490: The Near Infra Red Planet Searcher. The ESO New Technology Telescope (NTT) is an Alt-Az , 3.58-metre Richey-Chretien telescope which pioneered the use of active optics . The telescope and its enclosure had a revolutionary design for optimal image quality. NTT saw first light in March 1989. The telescope chamber is ventilated by a system of flaps which optimize the air flow across the NTT optimizing

5253-549: The SEST in 1987 (Swedish ESO Submillimetre Telescope), the only large submillimetre telescope in the southern hemisphere, which was a combined project between ESO and the Swedish Natural Science Research Council. Around the end of the century some of the original telescopes were closed: the 1m Schmidt closed in 1998 and the 1.5m in 2002, while new equipment owned by various foreign observatories

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5356-641: The Spanish founding of Santiago in 1541. Indeed, northern Mapuche groups appear to have responded to the Spanish conquest by abandoning their best agricultural lands and moving to remote parts away from the invaders. During the 17th century, the city suffered repeated attacks from privateers , including Francis Drake who opened the Pacific route to the English in 1578. Bartholomew Sharp , who partly burned and looted in 1680, and Edward Davis , who set fire to

5459-436: The aperture diameter for which the variance σ 2 {\displaystyle \sigma ^{2}} of the wavefront phase averaged over the aperture comes approximately to unity: σ 2 = 1.0299 ( d r 0 ) 5 / 3 {\displaystyle \sigma ^{2}=1.0299\left({\frac {d}{r_{0}}}\right)^{5/3}} This equation represents

5562-638: The atmosphere and thus not having any seeing problems and allowing observations of faint targets for the first time (although with poorer resolution than speckle observations of bright sources from ground-based telescopes because of Hubble's smaller telescope diameter). The highest resolution visible and infrared images currently come from imaging optical interferometers such as the Navy Prototype Optical Interferometer or Cambridge Optical Aperture Synthesis Telescope , but those can only be used on very bright stars. Starting in

5665-586: The atmosphere. The parameters r 0 and t 0 vary with the wavelength used for the astronomical imaging, allowing slightly higher resolution imaging at longer wavelengths using large telescopes. The seeing parameter r 0 is often known as the Fried parameter , named after David L. Fried . The atmospheric time constant t 0 is often referred to as the Greenwood time constant , after Darryl Greenwood . Mathematical models can give an accurate model of

5768-409: The background of the image on the left from June 1968. By 1976, the largest telescope planned, the § ESO 3.6 m Telescope , started operations. It was subsequently to have a 1.4m CAT (Coudé Auxiliary Telescope) attached. In 1984, the 2.2m telescope began operations, while in March 1989, the 3.5 m New Technology Telescope (NTT) saw first light . The program reached its apex with the installation of

5871-466: The beach has created a tourist residential development along the Elqui River . The most famous beach near La Serena is "Morrillos" with 25 km (16  mi ) of sand and dunes. In the southern part of Morrillos is Guanaqueros, a beautiful spot with calm waters. Water temperatures can reach 25 °C (77 °F) in summer. The best surf spot is Totoralillo beach with good waves. "El Cacho" wave

5974-416: The belief that there were canals on Mars . In viewing a bright object such as Mars, occasionally a still patch of air will come in front of the planet, resulting in a brief moment of clarity. Before the use of charge-coupled devices , there was no way of recording the image of the planet in the brief moment other than having the observer remember the image and draw it later. This had the effect of having

6077-404: The center for each telescope diameter. The diameter (FWHM) of the large blurred blob in long-exposure images is called the seeing disc diameter, and is independent of the telescope diameter used (as long as adaptive optics correction is not applied). It is first useful to give a brief overview of the basic theory of optical propagation through the atmosphere. In the standard classical theory, light

6180-400: The changes in the dancing speckle patterns is substantially lower. There are three common descriptions of the astronomical seeing conditions at an observatory: These are described in the sub-sections below: Without an atmosphere, a small star would have an apparent size, an " Airy disk ", in a telescope image determined by diffraction and would be inversely proportional to the diameter of

6283-519: The city being nicknamed "the city of the belfries". The Church Cathedral of La Serena was designated a Historical Monument in 1981. Construction was initiated by the French architect Jean Herbage in 1844, and dedicated in 1856. It is the largest temple in the city, constructed in Neoclassic style , measuring 60 metres (200 feet) long by 20 metres (66 feet) wide, with three central bodies. Inside there

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6386-453: The city later the same year on 26 August under the name of San Bartolomé de La Serena (now patron saint of the city), in the same place where the Plaza de Armas stands today. A few years later, on 4 May 1552, King Carlos I of Spain by royal decree gave it the title of city. One of the reasons to establish La Serena was to control Mapuche groups that had begun to migrate north following

6489-470: The city, giving it the nickname " The City of Churches ." Its traditional architecture consists of a series of housing and public buildings, of late 19th-century vintage style, built with wood from the US state of Oregon brought to Chile as counterweight in vessels sailing to the nearby port of Coquimbo to load copper and other minerals for transport back to the US. This Oregon pine and the use of adobe create

6592-516: The city. Between 1948 and 1952, president Gabriel González Videla prepared the Plan Serena , a project in which the city was renewed with investments and urban redevelopment that would imprint a single seal on the country. It began to take hold in the role of services, to rescue and to develop its own architectural style known as Colonial Revival . The city is the seat of the Roman Catholic Archdiocese of La Serena . The cathedral, built from

6695-529: The coast to the neighboring city of Coquimbo. As of the 2012 census, La Serena had a communal population of 198,164, and the Greater La Serena area had a population of around 400,000. As of the 2002 census (of the National Statistics Institute ) it had 160,148 inhabitants (77,385 men and 82,763 women). Of these, 147,815 (92.3%) lived in urban areas and 12,333 (7.7%) in rural areas. The population grew by 32.6% (39,332 persons) between

6798-584: The convent of Santo Domingo in 1686, caused great fear among the population, forcing the defence of the city in 1700. In addition to these attacks, the city was almost totally destroyed by the earthquake of 8 July 1730 . During the Revolution of 1859 , a rebellion against the conservative government, the city was taken by forces led by Pedro Leon Gallo . Gallo's forces were defeated at the Battle of Cerro Grande [es] by an army from Santiago, which then occupied

6901-516: The country, Mall Plaza La Serena, which has the national shops Falabella and París. Also Mall Puerta Del Mar, contains two supermarkets, and regional multistores, such as La Elegante, and shops for home and construction. The downtown is one of the places with major economic and financial institutions of the Coquimbo Region . The old part of the city is the largest and most important urban "traditional area" ( zona típica ) in Chile. The churches are distinguished by many styles of belfries , which led to

7004-513: The decision in 1963 to approve Chile as the site for the ESO observatory, scouting parties were sent to various locations to assess their suitability. The site that was decided upon was La Silla in the southern part of the Atacama Desert , 600 km north of Santiago de Chile and at an altitude of 2400 metres. Besides being government property, it had the added benefits of being in a dry, flat and easily accessible area, yet isolated and remote from any artificial light and dust sources. Originally named

7107-401: The dome and mirror seeing . To prevent heat input to the building, all motors in the telescope are water cooled and all the electronics boxes are insulated and cooled. The primary mirror of the NTT is actively controlled to preserve its figure at all telescope positions. The secondary mirror position is also actively controlled in three directions. The optimized airflow, the thermal controls, and

7210-544: The effects of astronomical seeing on images taken through ground-based telescopes. Three simulated short-exposure images are shown at the right through three different telescope diameters (as negative images to highlight the fainter features more clearly—a common astronomical convention). The telescope diameters are quoted in terms of the Fried parameter r 0 {\displaystyle r_{0}} (defined below). r 0 {\displaystyle r_{0}}

7313-525: The effects of the atmosphere will be negligible, and hence by recording large numbers of images in real-time, a 'lucky' excellent image can be picked out. This happens more often when the number of r0-size patches over the telescope pupil is not too large, and the technique consequently breaks down for very large telescopes. It can nonetheless outperform adaptive optics in some cases and is accessible to amateurs. It does require very much longer observation times than adaptive optics for imaging faint targets, and

7416-682: The ensemble average. For the Gaussian random approximation, the structure function of Tatarski (1961) can be described in terms of a single parameter r 0 {\displaystyle r_{0}} : D ϕ a ( ρ ) = 6.88 ( | ρ | r 0 ) 5 / 3 {\displaystyle D_{\phi _{a}}\left({\mathbf {\rho } }\right)=6.88\left({\frac {\left|\mathbf {\rho } \right|}{r_{0}}}\right)^{5/3}} r 0 {\displaystyle r_{0}} indicates

7519-417: The fractional change in wavefront amplitude and ϕ a ( r ) {\displaystyle \phi _{a}\left(\mathbf {r} \right)} is the change in wavefront phase introduced by the atmosphere. It is important to emphasise that χ a ( r ) {\displaystyle \chi _{a}\left(\mathbf {r} \right)} and ϕ

7622-442: The frequency of the light determined by ν = 1 π c | k | {\textstyle \nu ={\frac {1}{\pi }}c\left|\mathbf {k} \right|} , and A u {\displaystyle A_{u}} is the amplitude of the light. The photon flux in this case is proportional to the square of the amplitude A u {\displaystyle A_{u}} , and

7725-454: The genuine image of the city. There is also a number of remarkable and valuable small churches built of sedimentary stone quarried 5 km (3 mi) to the north of the Elqui River , having a characteristic color and texture formed by myriad small shells. These churches are all roughly 350 years old and have undergone restoration to varying degrees, bringing them back to their original form. San Francisco , San Agustín , Santo Domingo are

7828-400: The image of the planet be dependent on the observer's memory and preconceptions which led the belief that Mars had linear features. The effects of atmospheric seeing are qualitatively similar throughout the visible and near infrared wavebands. At large telescopes the long exposure image resolution is generally slightly higher at longer wavelengths, and the timescale ( t 0 - see below) for

7931-416: The interior zone of Vicuña and Ovalle . Today, the only railroad that passes through parts of the city carries iron ore from El Romeral mine to Guayacán's port in Coquimbo. The city relies on a bus station to provide transport from La Serena to most of the country, as well as an airport with daily flights to Santiago, Antofagasta, Arica, Copiapó and other destinations. Today there is a project to move

8034-403: The length-scale over which the turbulence becomes significant (10–20 cm at visible wavelengths at good observatories), and t 0 corresponds to the time-scale over which the changes in the turbulence become significant. r 0 determines the spacing of the actuators needed in an adaptive optics system, and t 0 determines the correction speed required to compensate for the effects of

8137-472: The long-term mean. As a commune, La Serena is a third-level administrative division of Chile administered by a municipal council , headed by a mayor who is directly elected every four years. Since October 2024, the city's interim mayor is Luis Henríquez. Within the electoral divisions of Chile , La Serena is represented in the Chamber of Deputies by Mario Bertolino (RN) and Marcelo Díaz (PS) as part of

8240-465: The names of a few of them. In 1920, he began to take shape a new economic boom in the mining of iron, attracting capital and human contingent, resulting in a further change in the urban structure. Currently, the city has its own architectural style (known as "neocolonial"), which is differentiated from other cities, preserving old buildings in colonial style, with many important National Monuments, mixing it with modern buildings but each one in turn follows

8343-407: The optical phase corresponds to the complex argument of ψ 0 {\displaystyle \psi _{0}} . As wavefronts pass through the Earth's atmosphere they may be perturbed by refractive index variations in the atmosphere. The diagram at the top-right of this page shows schematically a turbulent layer in the Earth's atmosphere perturbing planar wavefronts before they enter

8446-741: The papayas that are grown near La Serena in the Elqui Valley . Since 2007, there has been a professional tennis tournament, the Challenger de La Serena , on the courts of the Estadio Universidad del Mar , in which the first champion was the Argentine Mariano Zabaleta . The courts also hosted the Davis Cup series between Chile and Russia at the beginning of February 2007. The city of La Serena holds

8549-568: The petroglyphs there exists also a stone circle near La Silla, which is suggested as an astronomical tool. Three rocks aligned during the El Molle culture with Alpha Carinae , Beta Carinae and Alpha Centauri or Beta Centauri . This alignment occurred during late April and during May and could signal the beginning of the cold season. Farmers could have used this tool to determine when to move their herds, mostly camelidae , into their villages. There are signs of illicit excavations at La Silla since

8652-421: The phase fluctuations ϕ a ( r ) {\displaystyle \phi _{a}\left(\mathbf {r} \right)} . The amplitude fluctuations described by χ a ( r ) {\displaystyle \chi _{a}\left(\mathbf {r} \right)} have negligible effect on the structure of the images seen in the focus of a large telescope. For simplicity,

8755-759: The phase fluctuations in Tatarski's model are often assumed to have a Gaussian random distribution with the following second-order structure function: D ϕ a ( ρ ) = ⟨ | ϕ a ( r ) − ϕ a ( r + ρ ) | 2 ⟩ r {\displaystyle D_{\phi _{a}}\left(\mathbf {\rho } \right)=\left\langle \left|\phi _{a}\left(\mathbf {r} \right)-\phi _{a}\left(\mathbf {r} +\mathbf {\rho } \right)\right|^{2}\right\rangle _{\mathbf {r} }} where D ϕ

8858-419: The real part, and FT[] represents a discrete Fourier transform of the resulting two-dimensional square array (typically an FFT). The assumption that the phase fluctuations in Tatarski's model have a Gaussian random distribution is usually unrealistic. In reality, turbulence exhibits intermittency. These fluctuations in the turbulence strength can be straightforwardly simulated as follows: ϕ

8961-521: The regulatory framework in the construction of these structures which should each have features to maintain the colonial style of the city. In the center of the city until 2008, it is still not possible to identify buildings over eight stories high for a municipal status, however towards the coastal area of the Avenida del Mar, one begins to see a great real estate boom that is distinguished by high-rise buildings, ranging from La Serena running south and along

9064-495: The resolution of long-exposure images is determined primarily by diffraction and the size of the Airy pattern and thus is inversely proportional to the telescope diameter. For telescopes with diameters larger than r 0 , the image resolution is determined primarily by the atmosphere and is independent of telescope diameter, remaining constant at the value given by a telescope of diameter equal to r 0 . r 0 also corresponds to

9167-652: The road. On 25 March 1969, the ESO site at La Silla was finally formally inaugurated by President Eduardo Frei Montalva . With a permanent base of dormitories, workshops, hotels and several functioning telescopes, the observatory was fully operational. The ESO 1.5-metre and ESO 1-metre telescopes had been erected in the late 1960s, and were joined in 1968 by the Gran Prismo Objectif telescope, which had previously been used in South Africa. These three telescopes can be seen in this order from right to left in

9270-606: The same dimensions as R ( k ) , and where ⊗ {\displaystyle \otimes } represents convolution . The intermittency is described in terms of fluctuations in the turbulence strength C n 2 {\displaystyle C_{n}^{2}} . It can be seen that the equation for the Gaussian random case above is just the special case from this equation with: I ( k ) = δ ( | k | ) {\displaystyle I(k)=\delta (|k|)} where δ ( ) {\displaystyle \delta ()}

9373-428: The same stone and clade, dates from the 19th century. It must be said that although it lacks the same historical value as the older churches, this is a stone building in a country prone to seismic activity, and has survived various earthquakes. Indeed, during centuries of existence, there is almost no visible damage. All of these churches, along with others of minor importance, provide a unique urban landscape, an image for

9476-402: The seeing, as do wind and clouds. At the best high-altitude mountaintop observatories , the wind brings in stable air which has not previously been in contact with the ground, sometimes providing seeing as good as 0.4". The astronomical seeing conditions at an observatory can be conveniently described by the parameters r 0 and t 0 . For telescopes with diameters smaller than r 0 ,

9579-660: The size of an imaginary telescope aperture for which the diffraction limited angular resolution is equal to the resolution limited by seeing. Both the size of the seeing disc and the Fried parameter depend on the optical wavelength, but it is common to specify them for 500 nanometers. A seeing disk smaller than 0.4 arcseconds or a Fried parameter larger than 30 centimeters can be considered excellent seeing. The best conditions are typically found at high-altitude observatories on small islands, such as those at Mauna Kea or La Palma . Astronomical seeing has several effects: The effects of atmospheric seeing were indirectly responsible for

9682-524: The size of the telescope aperture . Today, many large scientific ground-based optical telescopes include adaptive optics to overcome seeing. The strength of seeing is often characterized by the angular diameter of the long-exposure image of a star ( seeing disk ) or by the Fried parameter r 0 . The diameter of the seeing disk is the full width at half maximum of its optical intensity. An exposure time of several tens of milliseconds can be considered long in this context. The Fried parameter describes

9785-491: The studies of turbulence by the Russian mathematician Andrey Kolmogorov . This model is supported by a variety of experimental measurements and is widely used in simulations of astronomical imaging. The model assumes that the wavefront perturbations are brought about by variations in the refractive index of the atmosphere. These refractive index variations lead directly to phase fluctuations described by ϕ

9888-399: The summer months, principally for the beaches, recreational activities, musical festivals, concerts, and Fashion Week . In addition, the city is an obligatory stop for hundreds of pilgrims that arrive to the city of Coquimbo, where during The Serenade they find lodging for visiting the zone and Valle de Elqui . In this city there are located branches of the more important chain stores of

9991-429: The summer season (January–February). La Serena has a cool desert climate , similar to nearby places in that it is clearly seasonal – in summer there is an absence of precipitation, but with abundant morning cloudiness and drizzle. which dissipates around noon, giving way to clear skies and 22 °C (72 °F) days. In winter, the temperatures descend to between 7 and 16 °C (45 and 61 °F). Being located in

10094-469: The telescope. However, when light enters the Earth's atmosphere , the different temperature layers and different wind speeds distort the light waves, leading to distortions in the image of a star. The effects of the atmosphere can be modeled as rotating cells of air moving turbulently. At most observatories, the turbulence is only significant on scales larger than r 0 (see below—the seeing parameter r 0

10197-401: The turbulence strength C N 2 ( h ) {\displaystyle C_{N}^{2}(h)} varies as a function of height h {\displaystyle h} above the telescope, and γ {\displaystyle \gamma } is the angular distance of the astronomical source from the zenith (from directly overhead). If turbulent evolution

10300-466: The type of adaptive optics system which will be needed at a particular telescope, or in deciding whether or not a particular location would be a good site for setting up a new astronomical observatory. Typically, several methods are used simultaneously for measuring the C n 2 {\displaystyle C_{n}^{2}} profile and then compared. Some of the most common methods include: There are also mathematical functions describing

10403-408: The vertical structure of the turbulence, in a technique known as Multiconjugate Adaptive Optics. Another cheaper technique, lucky imaging , has had good results on smaller telescopes. This idea dates back to pre-war naked-eye observations of moments of good seeing, which were followed by observations of the planets on cine film after World War II . The technique relies on the fact that every so often

10506-604: Was founded by captain Juan Bohón with the name " Villanueva de La Serena ". Although the exact date is disputed, probable dates include 15 November or 30 December 1543 and 4 September 1544. Many historians simply say that it was founded in 1544. Five years later, from the night of 11 January 1549 until the following day, a native uprising totally destroyed and burned the village, killing nearly every Spaniard. Pedro de Valdivia ordered Captain Francisco de Aguirre to re-establish

10609-518: Was introduced. A 1-metre telescope owned by Marseille Observatory opened in 1998, followed by a 1.2-metre telescope from Geneva Observatory in 2000. ESO operates three major optical and near infrared telescopes at the La Silla site: the New Technology Telescope (NTT), the 3.6-m ESO Telescope, and the 2.2-m Max-Planck-ESO Telescope (MPG/ESO Telescope). In addition La Silla hosts several other national and project telescopes such as

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