NightUp Castelldefels – About the project

About the project

Not being able to see the stars is just one of the many other consequences of light pollution: changes in ecosystems, wasted energy, effects on our health, etc.

NightUp aims to generate a tool that is useful to scientists and experts investigating this type of contamination.

Thanks to the collaboration of citizen scientists like you, we will create a color map of artificial light of Castelldefels that would help to better understand the impact of color on light pollution. If this first project is successful, it will be expanded globally to generate a map of the entire world.

[Updated to March 17, 2020]

Citizen scientists are making NightUp Castelldefels grow everyday: thanks!

By now we have more than 1100 photos in our database: thanks for making us reach our goal!

Click here or on the photo to look at the map of the contributions to the project.

We have started to analyze the data: in a few months we’ll publish here the results of the experiment. Stay tuned!

Light pollution

Light pollution is the sum of all the negative effects that artificial light has on the environment. This includes the impact of all that light that does not fulfill its purpose, such as when the lighting system is poorly directed or the light is too intense.

Artificial lighting has clear beneficial effects: it is difficult to imagine our life without the possibility of turning on the lights at night! We need artificial light in many situations, but it must be used correctly to limit its negative consequences.

About half the population of the European Union and more than two thirds of the US population live surrounded by so much artificial light, that at night they cannot observe the Milky Way with the naked eye. This type of pollution, in addition to preventing the enjoyment of a starry sky at night, also generates imbalances in ecosystems, has effects on people’s health and involves a cost of energy and money often unnecessary.

If you want to better understand the consequences of light pollution, you can find information in the websites of associations that fight against it, such as the International Dark Sky Association (, Cel Fosc ( /) or follow our collaborator Dr. Alejandro Sánchez de Miguel – researcher at the University of Exeter and expert in light pollution – on Twitter (@pmisson).

WHy NightUp?

All aspects of artificial light (intensity, color, direction of light, hours when the light is kept on, …) play their own role in the impact that light pollution can have. Therefore, detailed information on each of these aspects is needed to understand the role played by each of the parameters and have a complete and clear vision of the effects that artificial light can have on the environment and our health.

Currently, scientists have maps with information about the intensity of artificial light that allow them to make environmental impact studies in various areas of the planet. These data are obtained through images of the Earth made from satellites in space. The problem is that the devices that make these images can only obtain information about the light intensity, without any indication about its color.

However, in recent years it has been shown that the impact of light is different depending on the color. In general, it seems that lights with more blue components tend to have more negative effects than those that are more yellow or reddish. Therefore, scientists need a tool to investigate the relationship between the color of light and the different effects of light pollution.

The aim of NightUp is to help scientists generate a map of the color of artificial light in order to draw conclusions about the effects of the color of artificial light on living beings and ecosystems. Citizen participation is essential to obtain local and detailed information, which would be very complicated (and expensive) to obtain otherwise. With NightUp you can actively participate in a scientific experiment, contributing to progress in the search for solutions to a global problem, such as light pollution.

Image ISS028-E-26304 courtesy of the Earth Science and Remote Sensing Unit, NASA Johnson Space Center


To participate in NightUp, you have to take pictures of the various artificial light elements found in the streets, squares and roads of Castelldefels through the web application of the project. All images will be analyzed later, with the aim of generating a map of the color of the artificial light of Castelldefels. In this way, you can help scientists and experts in light pollution while discovering the night of Castelldefels from another perspective. Citizen participation is absolutely essential for this project to work. The more photos and participants, the better!


To participate in NightUp, you need a single measuring instrument: the smartphone camera. This is an unusual thing in a scientific experiment and is an important challenge for the project. To obtain valid and reliable results, scientists normally use under controlled conditions well-calibrated instruments designed for that purpose. In NightUp we extract information from photos taken with different instruments and that have not been designed for scientific research: the cameras of our phones. Being able to compare the information obtained with so many different instruments is essential, so that the data collected with NightUp have scientific validity to create a coherent map of light pollution and can be used for further research.

NightUp starts as a pilot project in Castelldefels to validate the method of data collection. If in this first phase we demonstrate that it is possible to gather information with the necessary scientific rigor, we will extend NightUp to the rest of the world, in order to create a global map of the color of artificial light. This would be a very useful tool to better understand the impact of this aspect of light pollution. By participating in NightUp Castelldefels you will become a pioneer of a global project!

the nightup app

You can contribute to NightUp directly from Chrome or you can download the application to your device.

We have designed NightUp to be the most respectful possible of your privacy: we ask you for permission to access your camera and your location just because it is the only way to extract the data we need to create the light pollution map. In any case, the data you send us is completely anonymous.

In addition, we have designed the app to require a minimum data flow, so that you don’t have to spend all your data to participate in the project.

We designed NightUp as a multiplatform progressive web application. Unfortunately, current versions of iOS do not support some of the software that is necessary to make NightUp possible.  However, future pending iOS updates should support NightUp. Give us your email through this contact form if you want us to notify you when iOS has been updated to support NightUp.

Analysis and results

We can reproduce any color on a digital screen starting from the three primary colors: red, green and blue. That’s why digital cameras record the intensity of these three fundamental colors for each pixel in the photo. The proportion between the intensity of red, blue and green light of the pixels in the halo of the light source will give us quantitative information about the color of the light of the photographed element.

You can help us to obtain more valuable and precise information by calibrating the camera of your device. But if you want to help us a little more, you can calibrate your camera: if you want to know how to do it, give us your email through the contact form and we’ll notify you when the calibration instructions are available.

Artificial intelligence algorithms will help us identify the position of the light source in the photo.

We will compare the information from each photo with the one from photos taken in nearby locations to validate the information. We will gather the information of all the photos received to create a map of Castelldefels divided into different regions according to the color of the light sources. This is a very valuable instrument for scientists studying light pollution, since they have very few data sources available with such resolution.

In summer 2020 we will publish the results of NightUp Castelldefels in the website of the project.


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