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What is the cutoff - southernmost - latitude for astronomical dusk - start of twilight - near the summer solstice?
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∙ 10y ago
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.
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∙ 10y ago
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Does it get darker than astronomical twilight in London England on nights near the June solstice?
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".
Is London England far enough south to get a completely dark sky - without astronomical twilight lasting all night near the summer solstice?
No.
Simple Question - Is there anywhere in England where astronomical twilight ends at night near June 21st?
No it only happens south of 48½ degrees north latitude.
Which country's southernmost point almost equals in latitude that for the southernmost limit of nautical twilight all night?
Denmark. Denmark's southernmost point is at approximately 54° 33' 32.7" N[1]. The southernmost limit (Northern Hemisphere) that nautical twilight could continue through local solar midnight for 2013, was at approximately 54° 33' 52.049" N[2] (calculated using true obliquity of the ecliptic). The latitude is approximately 598 metres or 654 yards further north than the southernmost point of Denmark. For 2014 54° 33' 54.232" N[2], approximately 666 metres or 728 yards further north than the southernmost point of Denmark. The next closest is the southernmost point of Scotland at approximately 54° 37' 59.85" N[3]. The southernmost limit (Northern Hemisphere) that nautical twilight could continue through local solar midnight for 2013, was at approximately 54° 33' 52.049" N[2]. The latitude is approximately 7.662 kilometres or 4.761 miles further south than the southernmost point of Scotland. For 2014 54° 33' 54.232" N[2], approximately 7.595 kilometres or 4.719 miles further south than the southernmost point of Scotland. 1. Sent to me from the National Survey and Cadastre of Denmark or KMS. 2. A Finnish Professor (Finnish Geodetic Institute) calculated the latitudes of the Arctic Circle to 2049, using True Obliquity of the Ecliptic. Furthermore GIT Barents website also uses True Obliquity of the Ecliptic for the Arctic Circle. A simple calculation (90° - True Obliquity of the Ecliptic at the 2013 Northern Hemisphere Summer Solstice 23° 26' 07.951" = Arctic Circle 66° 33' 52.049" N - Nautical Twilight when the centre of the sun is at a maximum of 12° below the horizon = 54° 33' 52.049" N) (90° - 23° 26' 07.951" = 66° 33' 52.049" - 12° = 54° 33' 52.049" N) gave me the latitude; using PHP Science Labs Obliquity of the Ecliptic and Nutation in Obliquity: 3. Scotland's southernmost point Mean High Water Springs, from 1:25,000 digital mapping software using Ordnance Survey mapping.
What is the northernmost latitude that can experience twilight between sunset and astronomical dusk on a single date of the year?
That is called The midnight sun which is a natural phenomenon occurring in summer months at places north of the Arctic Circle and south of the Antarctic Circle where the sun remains visible at the local midnight, around the solstice, June 21 in the north and December 21 in the south, and given fair weather the sun is visible for the full 24 hours.
Does the sky get darker than astronomical twilight on dates near the June solstice in Munich Germany disregarding light pollution?
No, astronomical twilight is the darkest stage of twilight where the Sun is between 12 and 18 degrees below the horizon. Near the June solstice in Munich, there may be some residual light in the sky even during astronomical twilight due to the high latitude of the location. The sky may not get significantly darker than astronomical twilight on those dates.
Does astronomical twilight end on nights near the summer solstice in Southampton England UK?
Astronomical twilight does not end on nights near the summer solstice in Southampton, England.
Does astronomical twilight end and night begin near the summer solstice in London or is that too far north?
Astronomical twilight lasts all night in London during the summer solstice, however due to the urban light pollution it is hardly noticeable.
Is 51 degrees north far enough south for astronomical twilight to end on dates near the summer solstice?
The Southern tip of Ireland is about 51 degrees North. That is not far enough South for astronomical twilight to end on dates near the summer solstice. (The Sun never sets at latitudes above about 66.5 degrees, at the summer solstice. Astronomical twilight ends with the centre of the Sun 18 degrees below the horizon. That means you would need to be around 48.5 degrees North to get full darkness at the summer solstice.)
Does it get darker than astronomical twilight in London England on nights near the June solstice?
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".
Is London England far enough south to get a completely dark sky - without astronomical twilight lasting all night near the summer solstice?
No.
Does it get darker than astronomical twilight in Newcastle-upon-Tyne England in June?
No because the latitude is 55 degrees N so the Sun never goes more than 11½ degrees below the northern horizon, so nautical twilight and astronomical twilight do not end.
Does astronomical twilight end near the summer solstice when observed from Greenwich England?
No, astronomical twilight does not end near the summer solstice when observed from Greenwich, England. On the summer solstice, which is around June 21st, astronomical twilight usually ends in the early morning hours before sunrise.
Between which two dates of the year does it never get darker than astronomical twilight at the latitude of the Arctic Circle?
April 3 and September 8
Is there anywhere in the Republic of Ireland that is far enough south for it to get completely dark at night near the summer solstice - without astronomical twilight lasting all night?
No there is not a place in Republic of Ireland that gets dark in the summer. You will have to have twilight for that to happen. _______________________________ The definition of "astronomical twilight" is that the Sun is 18 degrees or more below the horizon. On June 21, the summer solstice (plus or minus a day, depending on the cycle of leap years) the Sun reaches a latitude of 23 degrees 26 minutes (close enough to 23.5 degrees) north latitude. That means that when the Sun is over the central Pacific Ocean, the line of sunset is at 66.5 degrees north latitude north of Ireland. The southern tip of Ireland is about 51 degrees North; that means that at midnight on June 21, the Sun is only about 15.5 degrees below the northern horizon. Pretty close, but not quite low enough to be fully "dark".
Simple Question - Is there anywhere in England where astronomical twilight ends at night near June 21st?
No it only happens south of 48½ degrees north latitude.
Does it get darker than astronomical twilight at night in any part of Denmark around the June solstice?
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".
