Annual cycle of sunrise and nautical twilight at Tiputini.
Sunrise, the time when the edge of the sun first appears above the horizon, and nautical twilight, the time when the sun is 12º below the horizon, at the Tiputini Biodiversity Station (76°08’ W, 0°38’ S). Day 1 is January 1. Values were downloaded from the website of the US Naval Observatory (http://www.usno.navy.mil/USNO/astronomical-applications); they vary only 1–2 min from year to year. Curves are averages for years 2006–2013.