## 3 Results and Discussion
### Sky Characteristics and Photopic Descriptions
The presence of aerosol particles at certain times of the year could influence the presented SPD measures and, consequently, the subsequent calculations [25]. [PERSON] et al. [26] calculated the 25% and 75% interquartile values of the CCT to find the range containing 50% of the CCTs for each condition, obtaining  
Figure 3: CCT (K) measured depending on the season (from December 2018 to November 2019); orientation of north (**top**), east (**right**), south (**down**), and west (**left**); and elevation from the horizontal level of 15\({}^{\circ}\) (black), 30\({}^{\circ}\) (striped), and 45\({}^{\circ}\) (grey). a range for clear sky without aerosol particles of 5889-6294 K, a range for clear sky with aerosol particles of 5712-6325 K, and a range for overcast sky of 6218-7757 K. The overcast sky and atmosphere with aerosol particles represented extreme conditions where the limits of the CCT were observed. Daylight measured in Granada (Spain), with the most observed CCTs of 5555-5715 K [24], and in Boulder, Colorado (United States), with obtained CCTs of 5500-6400 K, showed that lower CCTs represented atmospheres with higher aerosol particle levels [23,24]. Similar results were found in Rochester, New York (United States), where daylight with CCT as low as 3530 K in a hazy sky was reported [27]. In Zaragoza, the mean CCTs obtained at 45\({}^{\circ}\) were 7574 K to the north (range 5660-12,380 K), 5377 K to the south (range 4954-5671 K), 5294 K to the east (range 5085-5543 K), and 8025 K to the west (range 5883-9587 K), irrespective of the presence of clouds, mainly due to the season and showing a broad range of daylight CCTs. Comparing our results with those previous results show very low rates of aerosol elements during all the seasons of the evaluated year. Luminance patterns of the 15 CIE standard skies have been described and used together with several skydome parameters including different illuminance levels or vertical sky components to classify daylight [1]. Sky luminance values have a strong dependence on its particular conditions such as clouds, which can vary in minutes; or the locations of measurement points that can have different conditions, even when they are nearby [28]. Therefore, the same categories of sky conditions, including clear sky, partly cloudy and overcast, cannot be considered to have similar luminance levels. We chose similar clear skies to perform our experiment, but the location of the sun, partially cloudy skies, and even the buildings of the surroundings highly influenced the results. At 15\({}^{\circ}\), values elevated enough to be considered to have been influenced by the buildings located around the measurement station can be observed (Figure 4). Despite this result, the highest luminance values were found at 45\({}^{\circ}\) at the nearby positions where the sun was placed during the measurements. Clouds influenced the measurements, as reflected in the September data, due to the presence of some clouds during the measurement (Table 1). Higher levels of photopic illuminance (Figure 5) are reached in the east orientation from March to August and in the south direction from September to March compared to the north and west orientations. The months with the highest photopic illuminance are generally in the summer months and in part of the spring months (from May to August), decreasing in the autumn and winter months in the east at the three elevations (15\({}^{\circ}\), 30\({}^{\circ}\) and 45\({}^{\circ}\)). However, in the south orientation, many differences in photopic illuminance are seen between the three elevations in the spring and summer months (from April to August), which become equal in the autumn and winter months (from September to March). These differences in the three elevations in spring and summer also occur in the north (from May to August). This does not happen in the west orientation, where the photopic illuminance at the three elevations is very equal during all months of the year.