Measuring darkness in remote places

Photometer SG-WAS. Credit: Miguel Rodríguez Alarcón (IAC).
Photometer SG-WAS. Credit: Miguel Rodríguez Alarcón (IAC).
Advertised on
Authors
SCIENCE COMMUNICATION AND OUTREACH UNIT
References
M. R. Alarcon, M. Puig-Subirà, M. Serra-Ricart, S. Lemes-Perera, M. Mallorquin,…

Completely autonomous, not invasive, and low-cost. This is the new SG-WAS (SkyGlow Wireless Autonomous Sensor) which will help to measure the impact of artificial night lighting on the natural protected areas of Macaronesia.

A little over a month ago, the magazine Sensors revealed to the scientific community a new low-cost instrument for measuring the brightness of the night sky. The SG-WAS photometer has been developed by the Canary R+D+I company SIELTEC Canarias, for the Project Interreg EELabs (Energy Efficiency Laboratories) coordinated by the Instituto de Astrofísica de Canarias (IAC). It is the first free standing sensor, powered by solar energy, which can communicate via the technologies LoRa, WiFi, or LTE-M. This allows it to be installed in places with very difficult access, where until now levels of light pollution could not be measured on the ground for long periods.

Outstanding among its technical characteristics is its rapid charging capability. It can attain maximum voltage in just four hours, after a complete night’s working. Thinking of its use on sites where the solar irradiation is very variable during the year, work has been put in to make it capable of remaining up to 20 days without recharging while it is taking measurements every night. And if after this length of time it is still not receiving sufficient sunlight in goes into hibernation, from which it can recover when it receives direct sunlight again.

For more than a year its resistance to extreme weather conditions has been tested, and the stability of its measurements has been shown during field tests. At the present time over 50 SG-WAS instruments are in action within the network of photometers of the EELabs project on the islands of Corvo (Azores), Maderia, La Palma, Gran Canaria and Tenerife, which take continual readings of the zenith darkness of the night sky every 5 minutes and send them to EELabs’ public data base.

Ciclo normal de carga-descarga de tres fotómetros SG-WAS versiones LoRa (verde), LTE-M (marrón) y WiFi (azul) ubicados en el Observatorio del Teide (OT, Islas Canarias, España).
Fig. 1. (a) Normal charge-discharge cycle for three SG-WAS photometers, LoRa (green) LTE-M (brown) and WiFi (blue) sited at the Teide Observatory (OT, Canary Islands, Spain). The solar irradiation, measured   by the meteorological station of the Stella telescopies is below. (b) Discharge curve for an SG-WAS WiFi when it is not exposed to direct sunlight (the photometer was inside the dome of a night-time telescope). It keeps on taking data for 20 days before going into hibernation. (c) Charge curve of an SG-WAS photometer once it is receiving direct sunlight after it is in hibernation.  (d9 curve of the apparatus 1*53 in the Valley of Tejeda (Grand Canary, Spain) which stopped being exposed to direct sunlight in mid-November, stayed in hibernation for 4 months, and started to work again when it received direct sunlight in March.

Innovation based on experience

Its optical design is very similar to the photometers TESS-W in the STARS4ALL project, in which the IAC also participated. “It is designed to measure the darkness in a circular area some 19 degrees in diameter around the zenith. It covers virtually the full visible range, between 400 and 720 nm, and has a transmittance slightly higher than its predecessors” explains Miguel R. Alarcón, IAC researcher and first author of the article. And he adds: “This has allowed us to design an averaging algorithm which lets us reduce the instrumental error down to thousandths of a magnitude and to recognize immediately the presence of clouds”.

To reach extreme precision “We have designed a new method of calibrating the photometers which uses a Sky Integrating Sphere (SIS) which lets us reach calibration accuracies below 0.02 mag/arsec2”, explains Miquel Serra-Ricart, coordinator of the EELabs project and coauthor of the article.

This work is an example of technology transfer between the Instituto de Astrofísica de Canarias and local industry, which is favoured by the projects in the Interreg MAC programme.

EELabs (eelabs.eu) is a project funded by the Programme INTERREG V-A MAC 2014-2020, cofinanced by FEDER (European Fund for Regional Development) of the European Union, under contract number MAC2/4.6d/238. Five centres in Macaronesia (IAC, ITER, ULPGC, SPEA-Azores and SPEA-Madeira) work in EELabs. The objective of EELabs is to build laboratories to measure the energy efficiency of the artificial night lighting in protected natural areas in Macaronesia (the Canaires, Madeira, and the Azores).

Scientific article: M. R. Alarcon, M. Puig-Subirà, M. Serra-Ricart, S. Lemes-Perera, M. Mallorquin, C. López (2021) SG-WAS: A New Wireless Autonomous Night Sky Brightness Sensor. Sensors 2021. DOI: https://doi.org/10.3390/s21165590

EELabs website: www.eelabs.eu

Related projects
Earth nigth
EELabs
EELabs (eelabs.eu) is a project financed by the INTERREG V-A MAC 2014-2020 Programme, co-financed by the FEDER (European Regional Development Fund) of the European Union, under contract number MAC2/4.6d/238. Five centres in Macaronesia work in EELabs (IAC, ITER, UPGC, SPEA-Azores, SPEA-Madeira).
Miquel
Serra Ricart
Closed
Related news
Astronomy Picture of the Day (APOD) on February 27th 2020
Press release
The natural brightness of the night sky
A recent study analyses data collected at 44 of the darkest places in the world, including the Canary Island Observatories, to develop the first complete reference method to measure the natural brightness of the night sky using low-cost photometers. Of the 44 photometers in the survey, the Roque de los Muchachos Observatory (Garafía, La Palma, Canary Islands) stands out at the darkest of all the skies analysed. The night sky is not completely dark; even in the remotest places there is a glow in the sky produced by natural components, both terrestrial and extraterrestrial, and by artificial
Advertised on
Night landscape in the Teide National Park. Total Eclipse of Moon and Red Tajinastes -endemic to Tenerife-. Image J.C. Casado @ starryearth.com.
Press release
EELabs: sustainable use of artificial lighting
Initiation of the European project EELabs. The recent visit of the Mayor of Gúímar to the Teide Observatory sees the start of the Energy Efficiency Laboratories project, coordinated by the Instituto de Astrofísica de Canarias, for the protection of night-time ecosystems through energy efficiency.
Advertised on
News type
Press release
Scope
Science and Technology
Outreach
Sky quality
Sky protection
Light pollution
General public
INTERREG UE
INTERREG_Eje MEDIO AMBIENTE

It may interest you

  • Merging binary
    Press release
    Astronomers find evidence that blue supergiant stars can be formed by the merger of two stars
    An international piece of research, led by the Instituto de Astrofísica de Canarias (IAC) has found clues to the nature of some of the brightest and hottest stars in our Universe, called blue supergiants. Although these stars are commonly observed, their origin has been an old puzzle that has been debated for several decades. By simulating novel stellar models and analysing a large data sample in the Large Magellanic Cloud, IAC researchers have found strong evidence that most blue supergiants may have formed from the merger of two stars bound in a binary system. The study is published in the
    Advertised on
  • Cadena de resonancias del sistema HD110067
    Press release
    The synchronized dance of a system of six planets is revealed
    An international collaboration, with participation by the Instituto de Astrofísica de Canarias (IAC), has found a system of six exoplanets orbiting a central star with a precise rhythm.This phenomenon, known as orbital resonance, is common during the starting phase of planet formation, but it is exceptional to find a system with such a large set of planets which conserves this kind of gravitational synchronism. This finding shows that the system has not undergone major changes during its six billion year history, so that it gives an unusual view of the formation and evolution of planets. The
    Advertised on
  • Observation of 2024 NP2 obtained with the TST telescope
    Press release
    The Solar System Group at the IAC discovers a new asteroid near the Earth
    The discovery of 2024 NP2 took place during the night of July 4th in images taken during the commissioning of the TST, a new telescope recently installed at the Teide Observatory. On July 4th the first regular observations were made in the commissioning of the Transient Survey Telescope (TST), an astronomical installation produced by a public-private collaboration between the IAC and the Canary company Light Bridges , at the Teide Observatory (Tenerife). The TST is a robotic telescope with a wide field. With a 1 metre telescope and a camera using an sCMOS detector at its prime focus, it can
    Advertised on