One of the Starlight Foundation “Astronomical Monitors and Guides” training courses took place at Sigüenza during the week of 28 of June. The Medieval City of Sigüenza has become one of the main tourist destinations in Castilla la Mancha. It was declared a Historic-Artistic Site in 1964. This small city has beautiful small streets that take us to a medieval period. Sigüenza is located in a rural region of Spain with dark skies that will probably be declared Starlight Reserve. 

ACTION researchers had the opportunity to teach about the impacts of Light Pollution and how to raise awareness to the citizens about this problem. During the practical work the students learned how to measure the sky brightness at night with photometers.  

Since we had 30 students (and some teachers) eager to collaborate, we proposed to map the entire city of Sigüenza using the StreetSpectra method. After the distribution of the diffraction gratings and some simple hands on instructions, the students took observations with their smartphones (see the attached map). 

Students map the street lights of Sigüenza

Some students with Prof. Zamorano after the observing and mapping the spectra of the street lights of Sigüenza. (Credits Jaime Zamorano)

The results (that we are analyzing at the time of writing this news) is that Sigüenza street lamps are mostly High Pressure Sodium (HPS) that provides the warm color to the medieval buildings and stone paved streets. Unfortunately, there are some streets with white Light Emitting Diode (LED) lights, some of them of 4000K, i.e, very blue. The good news is that there is also some warm amber LED lighting on some streets.

The nocturnal illumination of Sigüenza, that encourages a walk during the night, is threatened by a wild plan of ornamental lights at the Main Square and the Cathedral. Some citizens helped by researchers are fighting to reverse the excessive ornamental lighting. You can browse  ‘Adiós cielito lindo’  (opinion piece published in the local paper ‘La Plazuela’) with pictures that have been analysed to show the brightness increase.

Students map the street lights of Sigüenza_map

Map of Sigüenza with the positions where observations were taken. The inset picture shows one of the spectrum.