YozoraAtlas

How dark is the sky in Centre-Val de Loire?

Sky darkness for 5 towns and parks in Centre-Val de Loire, worked out from NASA satellite images of light at night (2025). None of them have skies of Bortle 4 or darker, where the Milky Way shows overhead. The darkest is Blois (20.05, Bortle 5), the brightest Orléans (19.26, Bortle 6). Milky Way season in Centre-Val de Loire runs May to July: on moonless nights the bright core stands clear of the horizon, climbing to about 14° at its highest.

19 Bortle class, 1 pristine to 9 city center park or dark-sky place city

Numbers like 21.95 or 16.97 are the brightness of the sky overhead on a clear, moonless night, in mag/arcsec². The scale runs backwards: a lower number means a brighter sky, from about 22 for a natural sky to about 17 in a city center.
How the readings are made

NASA satellite night-lights map of Centre-Val de Loire with every place marked

Darkest skies in Centre-Val de Loire

  1. BloisBortle 520.05
  2. ChâteaurouxBortle 519.95
  3. BourgesBortle 519.76

Among the places on this site. Plenty of land between them is just as dark, with no town or park to name it by.

Brightest city skies in Centre-Val de Loire

  1. OrléansBortle 619.26
  2. ToursBortle 619.31

All 5 places in Centre-Val de Loire

Amber names are parks and certified dark-sky places. The figure is the Bortle class: 1 darkest, 9 city center.
Blois5Bourges5Châteauroux5Orléans6Tours6