Complex sentence: John E. Bortle is the creator of the Bortle Scale to quantify the darkness of the sky from 1 (urban inner city) to 8 (extremely dark rural area or national park, usually at high elevation, low humidity, and low wind).
Split into simpler sentences: John E. Bortle is the creator of the Bortle Scale to quantify the darkness of the sky. The scale ranges from 1 (urban inner city) to 8 (extremely dark rural area or national park, usually at high elevation, low humidity, and low wind).