- Joined
- Dec 8, 2004
- Messages
- 4,812
Here's another simple trick to estimate how much time you have until sunset. This can be useful to know when gathering firewood, when to start looking for a campsite, or when to start heading back.
I took as much of the math out as I can. With luck, you won't need any at all.
First, this only works after midday. I don't mean noon--noon is the time on the clock. Midday is the point when the sun is halfway between rising and setting.
This can be adapted to determine time-till-sunset prior to noon, but you get into a little bit of adding there, and I'm trying to keep this easily memorable.
Also, this can work on a partly cloudy day, or even an overcast day provided you can see shadows.
All right. Ready?
Position yourself on relatively flat ground so that you can see an object and its shadow. A sign post, the roof line of a building, a cactus, a telephone pole, whatever. You could even put a stick into the ground if you're short of anything obvious.
Take a straight edge (ruler, walking stick, or fold a piece of paper in half) and hold it out so that you connect the very end of the shadow to the very top of the object casting that shadow.
Estimate the tilt in degrees. Remember: 90 is straight up (midday, in which case there would be little shadow), 0 is darkness, right? So halfway is 45 degrees. A third of that up is 30 degrees. Two-thirds up is 60 degrees... you probably have your own tricks.
Divide this by 15. That gives you the number of hours until sunset.
Example:
You see a dead tree with an obvious cracked limb in the distance. You can see the shadow of the limb on the trail ahead. Standing to the side, you pull out your folded map of the area. Holding your arms out, you use the map's straight folded edge to connect the shadow of the broken limb to the actual broken limb.
45 degree angle? Three hours until sunset.
60 degree angle? Four hours to sunset.
20 degree angle? One hour and twenty minutes to sunset.
15 degree angle? The shadows are very long, because you have only about one hour to sunset.
Caveats: again, in the morning, you need to go in the opposite direction to get to mid day, and then add 90 degrees to the result.
Also, remember that the sun is variably close to the South horizon (in the Northern Hemisphere) or the North horizon (in the Southern Hemisphere). As a result, your shadow might point more to the North or South, throwing off your calculation. But this only happens around midday--as you get closer to sunset, this method gets progressively more accurate. Frankly, in my opinion, that's when you'd need increasing accuracy.
Therefore, use this method to get a ballpark estimate until the shadow angle is about 30 degrees... then, you can get more accurate as you approach your two-hour-to-sunset window.
Hope this helps.
I took as much of the math out as I can. With luck, you won't need any at all.
First, this only works after midday. I don't mean noon--noon is the time on the clock. Midday is the point when the sun is halfway between rising and setting.
This can be adapted to determine time-till-sunset prior to noon, but you get into a little bit of adding there, and I'm trying to keep this easily memorable.
Also, this can work on a partly cloudy day, or even an overcast day provided you can see shadows.
All right. Ready?
Position yourself on relatively flat ground so that you can see an object and its shadow. A sign post, the roof line of a building, a cactus, a telephone pole, whatever. You could even put a stick into the ground if you're short of anything obvious.
Take a straight edge (ruler, walking stick, or fold a piece of paper in half) and hold it out so that you connect the very end of the shadow to the very top of the object casting that shadow.
Estimate the tilt in degrees. Remember: 90 is straight up (midday, in which case there would be little shadow), 0 is darkness, right? So halfway is 45 degrees. A third of that up is 30 degrees. Two-thirds up is 60 degrees... you probably have your own tricks.
Divide this by 15. That gives you the number of hours until sunset.
Example:
You see a dead tree with an obvious cracked limb in the distance. You can see the shadow of the limb on the trail ahead. Standing to the side, you pull out your folded map of the area. Holding your arms out, you use the map's straight folded edge to connect the shadow of the broken limb to the actual broken limb.
45 degree angle? Three hours until sunset.
60 degree angle? Four hours to sunset.
20 degree angle? One hour and twenty minutes to sunset.
15 degree angle? The shadows are very long, because you have only about one hour to sunset.
Caveats: again, in the morning, you need to go in the opposite direction to get to mid day, and then add 90 degrees to the result.
Also, remember that the sun is variably close to the South horizon (in the Northern Hemisphere) or the North horizon (in the Southern Hemisphere). As a result, your shadow might point more to the North or South, throwing off your calculation. But this only happens around midday--as you get closer to sunset, this method gets progressively more accurate. Frankly, in my opinion, that's when you'd need increasing accuracy.
Therefore, use this method to get a ballpark estimate until the shadow angle is about 30 degrees... then, you can get more accurate as you approach your two-hour-to-sunset window.
Hope this helps.
