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AZOTEA (Zenithal astronomy during & after the lockdown)

Measuring light pollution from home

Which is the impact of human activity in Light Pollution?

The brightness of the night sky varies depending on the lights on the street, the movement of cars and the activity of the offices. There is a sharp increase in darkness when, by law, the ornamental lights go out at 12 at night. This project tries to detect variations in this bright produced by the lock down to stop the advance of covid-19. From this difference the human contribution in sky brightness can be estimated.

Project opportunity

Due to the self-isolation we are experience, astronomical observation activities are reduced to those that we can carry out from our home with the instrumentation we happen to have with us.

This project proposes a study over time of the brightness and color of the night sky through measurements obtained at home with the help of DSLR cameras.

Checking the methodology

Sky brightness measurements of this project can be compared with those of professional instruments for the same night. This graph shows RGB measurements taken by Jaime Izquierdo with a SLR camera at Madrid city, measurements of the Johnson B, V, R photometric bands obtained by the AstMON-UCM instrument installed on the roof of the Facultad de Físicas UCM and measurements taken with TESS-W stars1 photometer from the city of Coslada.

Left: The data from the RGB channels of the camera adjust well to the astronomical photometry measurements (once scaled). This indicates that when we calibrate the cameras we will be able to use them to measure the evolution of the brightness and color of the night sky. The stars1 photometer data shows slightly different values as it is not located at the same place.

Right: All the observations gathered during a two-month monitoring period performed by the same collaborator using the same equipment configuration.

Monitoring the night sky during and after isolation

Our collaborators

This project is aimed at any DSLR camera owner who is interested. If you want to participate, please send us an e-mail to jzamorano@fis.ucm.es with your name, the place where you are going to carry out the measurements and your camera specifications.

Villaverde del Ducado (Guadalajara)

Canon 450D
Peleng 8 mm

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Canon 550D
Sigma 8mm

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Diego Rodríguez (AAM)

Villalba (Madrid)

Riba-roja de Túria (Valencia)

Nikon D5200

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Nikon 1 V1
Nikkor VR 10 – 30 mm f/3.5 – 5.6

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Canon EOS 1300D

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Canon EOS 200D
SAMYANG 8mm 1:3,5

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Pablo Javier Lucero

Rosario, Santa Fe, Argentina

Sony a7III

Víctor Curcó Murillo

Granollers i La Roca del Vallès

Canon EOS 77D
EFS 18-135 mm

Mollerussa (Lleida)

Canon 750D
18-55mm

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Olimpus OM-10
14-24 Micro 4/3

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Vitoria (Álava)

Canon 400D

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Instalation

The ideal situation for your station is a roof or terrace that allows a direct view of the Zenith (an imaginary point directly “above” a particular location, on the imaginary celestial sphere).

In the case of places outside large urban centers with a direct view of their light haloes, we would appreciate the the camera to record that glow. In that case the field of vision should cover the horizon and depending on the objective it will rise 30-45 degrees from there.

A camera shouldn’t be left in the open as it can be damaged by rain. To be able to measure in any situation we must a weather resistant camera housing case.

The easiest thing is to use plumbing PVC material. We will have to use something we have at home such as waterproff suitcases or plastic container boxes. A wooden box with a glass top secured with silicone may also work.

Configuration

We will take pictures along the whole night. To control the shooting you can use an intervalometer or a computer.

A sequence of one photo every 6-12 minutes is enough. We are working to create a platform for collecting and storing images, but, for the moment they will have to be stored on local disks.

  • Diaphragm: Select the most open or brightest diaphragm. (e.g. f/4 for a f/4 lens).
  • Sensitivity: For dark skies in rural locations ISO 800 or higher can be used. In light polluted urban areas it is better to use ISO 400.
  • Exposure: Exposure times in dark locations should be around 1 minute. For urban areas you will need to reduce the time so the pictures don’t saturate. 5s is a good value to start testing. Exposure time shouldn’t be less than 1s.
  • Focus: The focus should be set to the infinity like when we take astronomical pictures or landscapes. A perfect focus is not necessary as it is not a critical parameter.

Scientific analysis

During the processing of the images, the information will be decomposed into R, G and B channels so the flow will be measured in counts per second of the central area. This value will  be converted then into instrumental quantities that will allow the researchers to make graphic representations to show the evolution over time of the brightness of the sky and its color. All observations are processed with custom open software developed by our team.

Contact

Profesor Jaime Zamorano:
jzamorano@fis.ucm.es

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