document updated 9 years ago, on Sep 26, 2014
List of to-dos, the night before a hike:
- get a printed copy of:
- the trail map
- local sunset time
- the route to the trailhead — sunlight is precious, don't waste it driving/walking in circles
- refill backpack with water and food
(assuming you are still mostly packed from the previous trip)
- clip your toenails
- let someone know your planned route, and when you plan to be back
There are four different times given for sunset:
[2]
- sunset — The sun disappears below the horizon.
- civil twilight — The limit at which terrestrial objects can be clearly distinguished. This is the time that's enshrined in laws as the point at which drivers are required to turn on their headlights. The sun is 6° below the horizon.
- nautical twilight — Only vague outlines of objects are visible. Commonly referred to as "first light". It's difficult to see where the horizon is, and the sun is 12° below the horizon.
- astronomical twilight — When the sky becomes dark enough for astronomical observations. For someone working outside, there no real difference in darkness once nautical twilight passes, so this time is mostly meaningless to them. The sun is 18° below the horizon.
The amount of time between these varies as the length of the day itself varies: by season and latitude. It isn't simply "add 30 minutes to get one from the other", so consult the proper tables to know how long twilight lasts.
