Skies for Astronomical Observation

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2 Chapter 10 Skies for Astronomical Observation 1] Diagnosis: Skies for Astronomical Observation 401 2] Causes of the Degradation of the Quality of Skies 404 3] Actions to Preserve the Quality of Skies for Observation 413 Photograph: Gemini Sur

3 Skies LESS VISIBILITY OF THE STARS MORE VISIBILITY OF THE STARS

4 401 chapter 10 skies Introduction Abstract Chile s Northern Zone is characterized by its clean skies, which is why it has been chosen as the ideal place for astronomical observation. However, this characteristic is being threatened by light pollution, mainly caused by the public lighting of cities. Even though Chile has a regulation that establishes limits for public light emissions, the protection of the skies for astronomical observation requires the collaboration and understanding of the entire community. Model of the Giant Magellan Telescope (GMT). Diagnosis: Skies for Astronomical Observation 1 Model of the European Extremely Large Telescope (E-ELT). Northern Chile is known worldwide as the best region in the Southern Hemisphere for astronomical observations, due to the transparency and darkness of its night skies, which is a valuable national environmental and cultural heritage. This characteristic of the country s Northern skies has motivated, since the 1960s, the construction of several observatories, such as the ones at Cerro Tololo, Cerro La Silla, Las Campanas and Paranal, among others, with an investment of over 1,000 MMUSD. Thus, Chile is one of the countries that currently has the largest number of astronomical observatories on the globe and also where several of the most important astronomical megaprojects of the world will be established over the next few years, which brings about great international prestige in the scientific field. Model of the Large Synoptic Survey Telescope (LSST). This group of astronomical megaprojects that will be established in Chile over the next few years will allow the country to go from 40 percent to 60 percent of the total worldwide state-of-the-art facilities in this science.

5 Observatories in Chile Photograph: Guillermo Damke Table 1 Global Situation of Astronomical Projects in Chile Institution Telescope Place Association of Universities for Research in Astronomy, AURA Inc. Carnegie s Southern Hemisphere Observatory (CARSO) European Southern Observatory (ESO) Cerro Tololo π Víctor Blanco, with a diameter of 4 meters Cerro Pachón π Gémini Sur Project, with a diameter of 8 meters π SOAR, with a diameter of 4 meters Las Campanas. π Du Pont, with a diameter of 2.5 meters π Swope, with a diameter of 1 meter π Magellan Project, two telescopes, of 6.5 meters each La Silla π Several telescopes with diameters of up to 3.6 meters Valle de Elqui, Coquimbo Region Valle de Elqui, Coquimbo Region Vallenar, Atacama Region La Higuera, Coquimbo Region Cerro Paranal π VLT, four telescopes, with a diameter of 8 meters Tal-Tal, Antofagasta Region

6 Photograph: Igor Valdebenito Table 2 New Astronomical Projects in Northern Chile Institution Telescope Place Investment Implementation date Association of Universities for Research in Astronomy, AURA Inc. Cerro Pachón. Large Synoptic Survey Telescope (LSST), with a diameter of 8 meters Valle de Elqui, Coquimbo Region USD $500 million 2019 Carnegie s Southern Hemisphere Observatory (CARSO) Cerro Las Campanas. Giant Magellan Telescope (GMT), with a diameter of 24 meters Vallenar, Atacama Region USD $ 700 million 2018 European Southern Observatory (ESO) Cerro Armazones. European Extremely Large Telescope (E-ELT), with a diameter of 40 meters Antofagasta, Antofagasta Region $ 1,000 million Euros 2019 Source: OPCC, 2010.

7 404 chapter 10 skies for astronomical observation 2 Causes of the Degradation of the Quality of Skies The growth and development of cities and towns near astronomical observatories has placed the quality of the skies for observation in such places under serious risk, due to the growing emission of light towards the sky generated by public lighting of urban settlements, a phenomenon known as light pollution. In order to retain this environmental heritage, it is necessary to maintain the current levels of darkness of the night skies of the Antofagasta, Atacama and Coquimbo Regions. Figure 1 (dated 2000) shows the impact of light pollution coming from the cities of La Serena, Coquimbo, Andacollo and Vicuña. This area still has a clean night sky at the zenith, but is polluted towards the horizon, that is, there is a great risk of it no longer being completely dark in the next few decades. The blue color represents a small amount of artificial shine on the celestial sphere. Green represents a sky affected by the light of the crescent moon. Orange is equivalent Light Pollution in La Serena, Coquimbo, Andacollo and Vicuña. fig. 1 Tocopilla Mejillones Antofagasta Chuquicamata Calama Photograph: Perantonio Taltal El Salvador Chañaral Potrerillos Caldera Copiapó Huasco Vallenar La Serena Coquimbo Vicuña Andacollo Ovalle Los Vilos Illapel Salamanca

8 405 chapter 10 skies to having a full moon year-round, making the Milky Way practically invisible 1. Therefore, the preservation of astronomical quality is especially important for Chile and the international scientific and astronomical community, because the quality of observations and the permanence in our country of astronomical institutions in the long term directly depend on the control of light pollution. In fact, the IAU/ICSU/UNESCO Declaration on the Reduction of Adverse Environmental Impacts on Astronomy (Paris, 1992), specifically states that: The skies, which have been, and are, an inspiration to all humanity, are becoming obscured and even unknown to the younger generation. On the other hand, protecting the night sky is beneficial not only for astronomical observation (by scientists or amateurs), but also for developing astronomical tourism and for our own enjoyment of a starry sky, which has always been a key aspect for native peoples. It is worth mentioning that this problem is also present in other parts of the world. In the following photograph it is possible to see how most of the countries, of what is known as the First World, waste resources on illuminating the night sky. 1] Extract from P. Cinzano, F. Falchi (Padua University, Italy) and C.D. Elvidge (National Geophysical Data Center of the N.O.A.A, Boulder, USA). World Atlas of Artificial Light Cinzano, P. Falchi, F., Elvidge. CD The first world atlas of articial sky brightness, MNRAS. Source: OPCC.

9 406 chapter 10 skies for astronomical observation What is Light Pollution? Photographs: NSKY Light pollution is the brightness or shine of the night sky, generated by the reflection or diffusion of artificial light among the gases and particles of the atmosphere. Therefore, it is all exterior lighting (public lighting, ornamental lighting, advertisement lighting, lighting for sports or industrial lighting) that is not used to illuminate the ground and buildings, but rather is oriented towards the sky. Due to this problem, night darkness is diminishing and starlight is progressively dissapearing. There are several ways through which light can be dispersed throughout the line of vision, without necessarily being generated by a city directly visible from an astronomical observatory. Therefore, the only way to control light pollution is to reduce the amount of light that escapes towards the sky from urban settlements, some located even more than 200 kilometers away from the observatories.. Figure 2 shows how light pollution generated by cities affects the night sky, polluting the skies of a nearby astronomical observatory. Light that escapes towards the sky is dispersed by molecules or dust in the path of the beam of the telescope. The dimmer stars and galaxies, which are visible using a 4-meter telescope, are 40 times weaker than the natural emission of the night sky, which is why it is critically important to minimize light sources from nearby cities that add to the natural light emissions of the sky. Let us suppose that the luminosity of the sky, L, has a value equal to 1. If there is an increase of 20 percent, that is, L = 1.2, due to artificial light, it would imply that in the case of an 8-meter telescope its capacity would diminish to 7.63 m; whereas, if L = 2, a level of light pollution that doubles the luminosity of the natural environment, the capacity of the same telescope would be reduced to only 5.66 meters.

10 407 chapter 10 skies Light Dispersion fig. 2 Light Dispersion Light Dispersion Telescope City Light Pollution and Illumination Light is composed of a continuous spectrum of several color bands depending on its wavelength. The visible range for humans is located, on average, between 380 and 780 nanometers. However, in its extremes, our sensitivity is lower. Outside this range, it is simply impossible to see. Likewise, there is more sensitivity towards light in the spectral center. On the other hand, most of the astronomical observation carried out in Chile uses the same spectral range as humans.

11 408 chapter 10 skies for astronomical observation Visible Spectrum Diagram fig. 3 Diagrama del espectro visible Humans Humanos Insects Insectos 300 nm 400 nm 500 nm 600 nm 700 nm 800 nm Figure 3 shows a comparison of the spectrum of colors visible to humans and insects. Thus, a source of light that emits in wavelengths that humans cannot percieve, or where they have low sensitivity, does not have visual benefits for humans. Nevertheless, the emissions of certain lamps are located outside of this range, affecting insects and other species as well as astronomical observation. Emitting Sources The main emission source of light pollution is public lighting, followed by advertisement lighting. In some areas, industrial lighting is also a significant source of light pollution, particularly from factories that work around the clock. Light pollution generated by luminaires occurs for three main reasons: a) Because the light beam is not directed to the ground: It is caused due to the deficient screening of luminaires that emit direct light towards the sky, instead of using it to illuminate the ground and buildings, therefore, it does not illuminate what it should. Regarding this issue, sometimes the problem is caused due to a poor installation of the luminaires. b) Because the light radiation from the lamp is of a wavelength that the human eye cannot perceive: These are luminaires that emit extreme spectral ranges or a spectrum simply outside of what s visible to humans, thus wasting energy. c) Over-illumination: In the world, and also in Chile, there are standards that indicate maximum levels of lighting, depending on their use. However, when some cities replace luminaires, they do not consider these standards, using, for example, the same electric power for all public lighting, thus causing over-illumination. In some cases, light is reflected off the ground and other surfaces and, at the same time, is reflected towards the sky. The worst sources of exterior light for astronomy are those that emit a con-

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13 410 chapter 10 skies for astronomical observation INFRARED HUMAN VISION RANGE ULTRAVIOLET tinuous spectrum with several color bands that block the spectral information coming from dim cosmic objects. The sources that emit light in characteristic color bands are less harmful for observation, because they do not pollute the entire spectrum. However, some of these can be equally harmful, depending on the emission band. Figure 4 shows the standard sensitivity curve, that is, the range of visibility for humans and the area of the electromagnetic spectrum where the human eye is more sensitive in relation to the emission of light from different types of luminaires. π Sodium Lamps (first and second images): They do not emit ultraviolet light and they are twice as efficient, energy-wise, as a mercury lamp. Furthermore, low-pressure sodium lamps block astronomical observation very little (first image). π Mercury Lamps (third image): They emit a great amount of ultraviolet light, which diminishes their efficiency in the production of visible light and contributes to the brilliance of the sky. π Metal Halide Lamps with Ceramic Burners: They have a great color characterization, and do not over-pollute the electromagnetic spectrum. The implementation of this technology is more expensive in comparison to high-pressure sodium lamps. That is why its use is more restricted. π Solid State Illumination (LEDs): It presents several color options, with different impacts on the spectrum. The options commonly used now present high emissions on the spectral ranges that are used for astronomy (below 499 nanometers), thus being highly polluting for the night sky (Figure 5). Likewise, there are other warm white LEDs that, although they do not pollute the astronomical ULTRA observation spectrum as much, are less efficient for now in terms VIOLETA of illumination. However, several LED manufacturers are currently working to improve this technology for public lighting, therefore there might be adequate solutions designed for these types of requirements soon.

14 fig. 4 Examples of common emissions from several types of luminaires Low-Pressure Sodium High-Pressure Sodium Human vision sensitivity curve Mercury Steam Cool White LED (7,000 K) Warm White LED (3,200 K)

15 412 chapter 10 skies for astronomical observation + ASTRONOMY + SAFETY The use of more efficient technologies and a proper installation of luminaires does not only provide benefits for astronomical observation, but it also improves illumination in the cities, which contributes to citizen safety. Likewise, it reduces energy costs for municipalities and companies. There is currently a luminaire replacement program in the Antofagasta, Atacama and Coquimbo regions. However, official information is not available on the total number of public luminaires in these regions. According to the Electricity and Fuel Superintendence based on reports of the respective municipalities-, until 2011, this program recorded a progress of 70 percent in the Antofagasta Region, 57 percent in the Atacama Region and 54 percent in the Coquimbo Region. In addition, there are several replacement projects currently being designed or tendered.

16 413 chapter 10 skies Actions to Preserve the Quality of Skies for Observation 3 The installation of astronomical observatories in Chile has been made effective through agreements signed between the Chilean Government and the responsible organizations. Among these, it is important to mention that the Cooperation Agreement between the Government of the Republic of Chile and the European Organization for Astronomical Research in the Southern Hemisphere (ESO) for the Establishment of an Astronomical Observatory in Chile, of 1995, indicates under article eight: 1. The Government and the ESO will adopt all of the measures necessary within their competence to maintain and protect the astronomical and environmental qualities of the observation centers installed or to be installed by the ESO. In order to do this, a Joint Committee will be established, who will provide pertinent recommendations. 2. This Committe will be formed by representatives of the Ministry of Education, the National Commission for the Environment (CONAMA), by members of the scientific community appointed by the Ministry of Education and ESO representatives. The Committee will pay special attention to light pollution and particle pollution issues as well as to the control of environmental impacts of mining activities, considering the guidelines of the International Astronomical Union and current Chilean environmental laws. As a result of the work of the AURA and CONAMA, supported by CARSO and the ESO, background information was compiled to develop an environmental standard aimed at regulating light pollution, with the objective of protecting the quality of skies in the northern zone of the country. Thus, the Emission Standard to Regulate Light Pollution has been in force since Some international regulations were considered as background information to develop the standard: π Law 31/1988 on the Protection of the Astronomical Quality of Observatories of the Astrophysics Institute of Canarias and the Real Decree 243/1992, through which the regulation of the mentioned law was approved. π Ordinance An Ordinance Amending Chapter 14, Article 9, of Hawaii County Code 1983, Relating to Outdoor Lighting.

17 414 chapter 10 skies for astronomical observation Although these regulations served as basis, there was also innovation on important aspects, adapting the standard to the legal and technical national reality. Emission Standard for the Regulation of Light Pollution Supreme Decree Nº 686/1998, Ministry of Economy The objective of the light standard (as it is known) is to protect the astronomical quality of the skies of the Antofagasta, Atacama and Coquimbo regions, by regulating light pollution. It is expected that it will help preserve the quality of the mentioned skies and avoid future deterioration. It is worth noting that this standard only has territorial application in these regions, but it has been considered to analyze a future possibility of expanding it to the entire country. The inspection agency for this standard is the Electricity and Fuel Superintendence (SEC, by its acronym in Spanish). In order to regulate light pollution, this standard considers two basic criteria: π Avoiding the emission of light towards the sky by using leveled screened luminaires. π Avoiding the emission of light using a range of visibility not perceived by the human eye (only useful spectrum), because that light spectrum affects astronomical observation. π Sources Regulated by the Standard The sources that must comply with this standard are those classified as Outdoor Lights, which refers to luminaires set up with fixed or sporadic installations, in open facilities for nocturnal use. These include, for example, public lighting, ornamental lighting, park lighting, lighting in sport and recreational facilities, signs, lighting in industrial facilities, safety lighting and outdoor lighting of buildings and condominiums. This standard is not applicable for the following sources: π Combustion of natural gas or other fuels. π Ornamental lighting used in festivities (less than 60 watts) π Aerial and maritime navigation π Motor vehicles π Traffic safety π Showcases π Laser projectors for astronomical purposes π Lighting in closed spaces π Sport facilities, sign lighting (less tan 140 watts)

18 Photograph: Pedro Sanhueza

19 416 chapter 10 skies for astronomical observation Table 5 Type of Luminaires 1. Public, industrial, minning, condominiums, parking lots, companies, private buildings 2. Projectors and garden lighting, beaches, parks; ornamental lighting of buildings and monuments 3. Sport and recreational (*) 4. Advertisement and signs (*) (**) Nominal Luminous Flux (NLF) <= 15,000 lm > 15,000 lm <= 9,000 lm. > 9,000 lm Upper Hemispheric Flux (UHF) <= 0.8 % <= 1.8 % <= 5 % According to type 1. Luminous Effectiveness >=80 lm/watt >=80 lm/watt Nonexistent According to type 1. Nonexistent Nonexistent Nonexistent Nonexistent Nonexistent Nonexistent 5. Laser Projectors (*) Nonexistent Nonexistent Nonexistent 6. Facilities of companies, exterior areas of private buildings 7. Outdoor luminaires over 140 lumens/watts Maximum Levels Allowed in the Standard According to type 1. According to type 1. According to type 1. Time Restriction No restriction No restriction Subjected to type 1 from 2 A.M. From 1 A.M. they cannot emit an UHF greater than 0.8 percent of their NLF. From 2 A.M. projectors must be adjusted below the horizontal No restriction No restriction No restriction No restriction No restriction (*) The schedule mentioned in types 3, 4 and 5 will be in force one our after the stipulated time, on Saturdays, Sundays and holidays. (**) This percentage will not be applicable for advertisement and signs located inside shopping centers while they are open to the public. RELEVANT CONCEPTS Nominal Luminous Flux: Flux determined by the manufacturer and measured in lumens Upper Hemispheric Flux: Flux of light that escapes towards the sky. Luminous Effectiveness: Relationship between the flux emitted by a source of light and the electric power unit used to obtain it. Radiant Flux: Physical unit of radiation that corresponds to radiated watts, radiated power. It is an energy unit and, therefore, independent from an observer. Lumen (lm): Psycophysical unit. It is measured according to the sensations of a human being and transformed into numbers according to a statistical array that determines our vision limits. It refers to the light perceived by humans.

20 417 chapter 10 skies The requirements of the standard are applied through the following: π The photometric certification of the characteristics of the lamp, by a laboratory recognized by the SEC (by its acronym in Spanish). π Checking the proper installation of lamps, and π A time restriction applicable for signs and advertisement, sport and recreational facilities. π Implementation of the Standard In order to implement this standard, an application manual was developed and the Office for the Protection of the Quality of the Skies (OPCC, by its acronym in Spanish) was created, in 1999, through an agreement between CONAMA and the AURA, CARSO and ESO astronomical organizations. This office, located in La Serena, has the main objective of disseminating the standard in seminars, international conferences and technical dissemination lectures. At the same time, this office has supported luminaire replacement projects and has prepared a Practical Guide for Outdoor Lightning. π Inspection of the Standard The SEC has carried out specific inspections to certify the compliance of the standard. However, this has not been systematic since some difficulties have arisen, mainly related to the lack of standardized measuring instruments, and the unavailability of inspectors for night shifts and the poor judicial certainty on the penalties. Due to these difficulties that have been explained by the inspection agency, there is neither an official registry of luminaire replacement, nor reports about the compliance status of this standard in the private sector. On the other hand, as in all of the other environmental standards, the light standard is required by the Environmental Impact Assessment System for every project that involves outdoor lighting, such as those in the mining sector. These projects report the compliance of the standard and also deliver a photometric certificate of the luminaires. π Economic Benefits The results obtained from the first experiences of replacing polluting luminaires with more modern ones that meet the Supreme Decree N 686/98 in the Coquimbo Region: Vicuña and La Serena are presented below.

21 418 chapter 10 skies for astronomical observation Table 6 Luminaires Replaced / Modified Replacement of Luminaires in Vicuña 1,534 Before 7,800,000 lumens Illumination After 8,900,000 lumens Result 14% Increase Before 210,000 watts Luminaires replacement in Las Delicias Av., Vicuña. Installed Power (estimation) After 110,00 watts Result 48% Reduction Power Loss (estimation) Before 24,000 watts After 1,100 watts Result 95% Reduction Source: Enrique Piraino, UCV-consultant OPCC (2002) As a result of this replacement, a reduction in 50 percent of energy use was achieved, the illumination is twice as intense, there was a decrease in glare blindness and 50 times less light pollution. π Compliance with the light standard in Northern Chile After Before

22 419 chapter 10 skies Table 7 Replacement of Luminaires in La Serena π Result of the Replacement of Luminaires Replaced / Colonial Lanterns in La Serena Modified 5,692 Before Before 32,700,000 lumens Illumination After Result 58,400,000 lumens 68% Increase Installed Power (estimation) Power Loss (estimation) Before 810,000 watts After 660,00 watts Result 19% Reduction Before 161,000 watts After 11,700 watts Result 93% Reduction Source: Enrique Piraino, UCV-consultant OPCC (2002) After The investment made for the replacement of luminaires has allowed the quality of the night sky to be protected in Northern Chile, and has also generated significant savings in terms of energy consumption. Photograph: Pedro Sanhueza

23 420 chapter 10 skies for astronomical observation π Revision of the Light Standard In 2011, the Ministry of the Environment began a revision process of the Emission Standard for the Regulation of Light Pollution Supreme Decree N 686/98 Ministry of Economy. The aim of this revision is to significantly restrict direct emissions of light towards the night sky, through greater control of reflected light and energy consumption, while at the same time controlling the most damaging spectral radiations to astronomy. In addition, another purpose is to regulate advertisement and sports-related lighting at all times of day. All of which can be done, considering that less polluting technologies have been available for several years and that in some countries they are being used on a daily basis. The new version of the draft bill of the revision of the standard, prepared with the support of the OPCC and other national and international organizations (Astrophysics Institute of Canarias (IAC by its acronym in Spanish)/Technical Office for the Protection of the Quality of the Sky (OTPC by its acronym in Spanish), Cielo Buio Italia, Universidad Nacional de Tucumán), was published in the Legal Gazette for public consultation, on January 15, Today, work is being carried out to gather and process all of the observations made during that period and also on possible adjustments to the draft bill to be able to move on to the elaboration of the final project. The revision of this emission standard will allow to improve Chile s current global position in terms of night sky protection, matching standards and laws currently in force in Hawaii, the continental United States, a large part of Italy and the Canary Islands, Spain.

24 421 chapter 10 skies References Cinzano, P.; Falchi, F. (Universidad de Padua, Italia) and ELVIDGE, C.D. (Centro Nacional de Datos Geofísicos de la N.O.A.A. Boulder, USA). Accepted 2001, July 27. Received 2001, July 24; in original form 2000 December 18. The first world atlas of the artificial night sky brightness. Royal Astronomical Society. Comisión Nacional del Medio Ambiente (CONAMA), Análisis general del impacto económico y social del anteproyecto de norma de emisión para la regulación de la contaminación lumínica. Santiago: CONAMA. Comisión Nacional del Medio Ambiente (CONAMA), Expediente público proceso elaboración Decreto Supremo N 686/98 del Ministerio de Economía-Norma de Emisión para la regulación de la contaminación lumínica. Santiago: CONAMA. Comisión Nacional del Medio Ambiente (CONAMA), Informe de actividades. Oficina de Protección de la Calidad del Cielo del Norte de Chile. La Serena: CONAMA. International Astronomical Union, The International Council for Science and the United Nations Organization for Education, Science and Culture (IAU/ICSU/UNESCO), Declaration on the Reduction of Adverse Environmental Impacts on Astronomy of the meeting IAU/ICSU/UNESCO. Paris.