There is still light reflecting off the earth's atmosphere after sunset. Officially, twilight ends at 18 degrees below horizon, when it is completely dark, although at 15 degrees it is dark enough!
If a star's azimuth is 90 degrees, it is located directly east on the horizon. An altitude of 45 degrees means that the star is positioned halfway up in the sky, forming a right angle with the horizon. Therefore, this star would be visible in the eastern sky at an angle that is halfway between the horizon and the zenith.
33 degrees perpendicular to the horizon
The Sun advances 15 degrees an hour; that is, 15 degrees every 60 minutes. You can base your calculations on that. If you live near the equator, after sunset the Sun will move directly downwards; if you live at higher latitudes, for example in Europe, the Sun moves at an angle, so while it will still move (for example) 15 degrees in an hour, it will not be 15 degrees below the horizon.
If the sun is 40 degrees above the horizon, a 5-ft person casts a shadow 5ft 11.5in long (rounded)
A star at 358 degrees is located just 2 degrees west of true north on a compass. This means it is positioned slightly to the northwest, very close to the northernmost point. In terms of celestial navigation, it would be near the horizon in the northern sky.
The sun being nine degrees below the horizon indicates that it is in the civil twilight phase. At this point, there is still enough light for most outdoor activities without the need for artificial lighting.
Twilight is when the sun is below the horizon- either has not yet risen, or has just set. Civil twilight- what most people mean when they say twilight- the sun is no more than 6 degrees below the horizon. There is also nautical twilight, where the sun can be as much as 12 degrees below the horizon. That time is used by sailors to take "sightings" on stars with a sextant for navigation. In Nautical twilight, you can see stars, but there is still a visible horizon to use in your sightings.
Twilight is when the sun is below the horizon- either has not yet risen, or has just set. Civil twilight- what most people mean when they say twilight- the sun is no more than 6 degrees below the horizon. There is also nautical twilight, where the sun can be as much as 12 degrees below the horizon. That time is used by sailors to take "sightings" on stars with a sextant for navigation. In Nautical twilight, you can see stars, but there is still a visible horizon to use in your sightings.
When the Sun is 18 degrees below the horizon.
Here's the formula: From sunset until the Sun is six degrees below the horizon is civil twillight. It's still light enough to read. When the Sun is six to twelve degrees below the horizon is nautical twilight. One can still see the horizon at sea; that is, tell when the sea stops and the sky starts. From twelve to eighteen degrees is astronomical twilight, which is when the stars start to come out. After the Sun is more than eighteen degrees below the horizon, it's officially Night.
The altitude of the horizon is 0 degrees. This is because the horizon is considered to be at eye level, so it is equivalent to the observer's horizontal line of sight.
4. The first one is called Twilight. The second one is called New Moon The third one is called Eclipse. The fourth one is called Breaking Dawn. Plus there is a novella called The Second Life Of Bree Tanner.
The definition of "astronomical twilight" is when the Sun is more than 18 degrees below the horizon. At latitudes above 48.5 degrees, the Sun is less than 18 degrees below the horizon, even looking straight north (or south, for the southern hemisphere) at midnight on the solstice.
No, 56 degrees above the horizon isn't "low". "Low in the sky" is less than 20 degrees elevation or so.
At the summer solstice the sun sets on the northern horizon at latitude 66.6 degrees north. At the same time astronomical twilight ends only at latitudes below 48.6 degrees north. It's 66.6 minus 18 because for astronomical twilight to end the Sun's centre must be 18 degrees below the horizon.
Wikipedia sez: "Astronomical twilight is defined to begin in the morning, and to end in the evening when the center of the Sun is geometrically 18 degrees below the horizon." London, England is at 51 degrees north latitude. At midnight in the June Solstice, the Sun is at a declination of 23.5 degrees (approximately), so the over-the-pole angular distance is (90-51) + (90-23.5) degrees, or 105 degrees. The horizon is 90 degrees, so the Sun is 15 degrees below the northern horizon at midnight on June 21. So, no, it won't meet the definition for "darker than astronomical twilight".
No. The southern border of Denmark is at 54 degrees 44 minutes north.Wikipedia sez: "Astronomical twilight is defined to begin in the morning, and to end in the evening when the center of the Sun is geometrically 18 degrees below the horizon."At midnight in the June Solstice, the Sun is at a declination of 23.5 degrees (approximately), so the over-the-pole angular distance is (90-54.5) + (90-23.5) degrees, or 102 degrees. The horizon is 90 degrees, so the Sun is 15 degrees below the northern horizon at midnight on June 21.So, no, it won't meet the definition for "darker than astronomical twilight".