Lux T RH during eclipse
Taken by Lorenzo Comolli on August 12, 2026 @
Villahoz, Spain
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Details:
A solar eclipse greatly influences Earth's atmosphere. The temperature, relative humidity, and luminance data show typical trends, unique to each eclipse and location.
For this event, I used a T/RH datalogger with the sensors positioned 1 meter above the ground on a small tree, with sensors shaded from direct sunlight.
During this eclipse, I recorded a temperature drop of only 2°C compared to the baseline trend, versus 5°C in Arkansas (2024), 9°C in Wyoming (2017), 4°C in Egypt (2006), and 7°C in Hungary (1999). Clearly the eclipse near the horizon greatly reduced the temperature drop.
A digital luxmeter measured the horizontal luminance: this is a really interesting measurement, which shows the tremendous fall in light, dropping between full Sun at 30000 lux at C1 and totality at only 1.7 lux (to be compared to 1.8 lux in Arkansas 2024, 3.4 lux in Wyoming 2017, 4.1 lux in Egypt 2006). This is the lowest value among my historical measurements, clearly due to the low altitude Sun, although I expected an even lower value due to the Sun's low altitude; this is nearly similar to Arkansas 2024 with the eclipse very high in the sky. Maybe the shorter duration of the totality (only 1 min 45 s) was the key factor. Further analysis needed!
During totality I measured the sky brightness with an SQM-L, obtaining 14.29 mag/arcsec², which is equivalent to the twilight sky when the Sun's altitude is -6°, i.e. civil twilight. Want to know how dark the sky gets during totality? Just wait for civil twilight—about 30 minutes after sunset!
Photographer's website:
https://comolli.astrosurf.com/ecl26a.htm
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