astronomical twilight in a sentence

Examples

1. This is followed by the nautical twilight, when the sun is 6?and 12?below the horizon ( heights of between  " 6?and  " 12?), after which comes the astronomical twilight, defined as the period from  " 12?to  " 18?
2. From a point on the ground at this latitude, the sun is above the horizon for 16 hours, 12 minutes during the summer solstice and 8 hours, 14 minutes during the winter solstice This latitude also roughly corresponds to the minimum latitude in which astronomical twilight can last all night near the summer solstice.
3. :Though not directly relevant to the question, the uncertainty of the boundaries of night and day is underlined by there being three differingly defined twilights : Civil twilight, Nautical twilight and Astronomical twilight, which begin or end when the Sun is 6, 12 or 18 degrees below the horizon respectively . { The poster formerly known as 87.81.230.195 } talk ) 13 : 24, 27 December 2016 ( UTC)