What is the difference between civil twilight, astronomical twilight, and nautical twilight?
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I was a Navigator in the US Navy recently and so I was taught all of this but I did not use it practically.
As we head into night from day—–>
Civil Twilight – The sun has set (aka gone below the horizon) but it is still bright enough to see without artificial light.
Nautical Twilight – The sun has traveled further below the horizon and you can no longer see activities without artificial light. More importantly, their is enough light that you can still make out the horizon, but, with the drop in light you can now see stars and planets. This is important because to use astronomical bodies for navigation you must be able to see the star/planet and the horizon to utilize a sextant.
Astronomical Twilight – (We didn’t use in the Navy Navigation course) Seems to be a special distinction astronomers make between a time when, without light pollution, you can only make out the brighter, more visible stars and planets. Once this period is over, the sun’s light is no longer visible and all of visible astronomical bodies should be observable.
The corresponding angles with respect to the horizon are all on Wikipedia.
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