Sundial Facts - Kent Sundials

Kent Sundials - Sundials designed and made in England

Sundial Facts

4th July 2011 - North comes in 3 'varieties'. True North (also called solar North), compass North and Grid north (as the grids on an ordanance survey map). Sundials must be set to true north to be accurate. An OS map will often tell you on the boarder what the difference is between compass north and true north where you are, good enough for setting a sundial. My information page tells you how to find true north.

28th May 2011 - Zenith - often used to describe the moment at which the sun reaches its highest point in the day (noon) but in its pure meaning Zenith is the point when the sun is directly over head, an occurrence only possible in the tropics. ( Russell Crowe uses the term in Master and Commander' as he gives a sextant class to the midshipman)

7th May 2011 - A pole place vertically into the ground will always cast a shadow in the UK. Even on midsummers day, 21st June, the sun will not be directly overhead at noon so the pole will still cast a small shadow. To enjoy 2 days in the year when a vertical pole would cast no shadow at noon you have to live between the tropics of capricorn and cancer.

17 - Sunset and Sunrise - obvious really, but the Sun rises the same time in hours before noon as it sets after it. So if sunset is at 4.30pm, which is 4 and a half hours after noon, it will rise at 7.30am, 4 and a half hours before noon.

16 - New grange is a neolithic passage tomb in Ireland, about 5000 years old. On the morning of the winter solstice (the shortest day) the Sun rises in an alignment with the passage into the tomb and strikes the back wall of the main cruciform shaped chamber. Why choose the Winter Solstice? why not summer or equinox? Maybe after the hard dark days of winter it was important to recognize that days were getting longer again? Very 'Indiana Jones' and well worth a visit.

14 - Local Noon is when the sun is directly overhead where you are. Where I live in Ashford Kent it is local noon about 4 minutes before it is noon by my watch (Greenwich Mean time) because Ashford is about 1 degree East of Greenwich. If a football pitch lies east to west the local time difference from one goal to the other will be about a quarter of a second, this is why we all live in time zones rather than use local time.

12 - We have seasons because the earths axis tilts at 23.5 degrees. As we go around the sun we tilt toward it, giving us summer and 6months later away, giving us winter. If the earth was not tilted on its axis we wouldn't have seasons.

36 - Your watch can act as a pretty good compass. Stand with your watch face horizontal and move your wrist until the hour hand faces the Sun. Due south is the direction being pointed at by the 12 o'clock mark.

35 - The Sun is in the same place every day at the same time. When you view the sun at a fixed point from your home or any other consistent point it will always be at the same position. In the summer it will be higher in the sky and in the winter much lower, but always in the same place. The sun will be below the horizon early and late on winter days so not visable but will be in the same place in the summer but above the horizon because the northern hemisphere tilts more toward the sun in the summer.

34 - Mass produced sundials are made to suit a general latitude and can therefore never be accurate as a sundial must be made to suit the latitude it is to be located at. In the past many were made in the industrial midlands so they were set at about 52 degrees north, not too bad for most UK sites. Today many come from China, so the latitude they are made to suit could be ?!??!!
Is there anything more disappointing than a truly inaccurate sundial?

33 - the Babylonian hour - You may have heard this term used on certain sundials, it means the hours since the sun has risen and can be found on many old sundials. If the sun rose at 4am and it is midday the Babylonian hour is 8.

32 - 12 'hour' days - In the ancient days of Greece and Rome the days were divided into 12 'temporal' hours. As days were determined by sunrise and sunset the hours varied in length depending on the season. Around the equinoxes you would of course get around 60 minutes in each temporal hour but in winter each hour could be as short as 40 minutes. Therefore, in ancient texts if they refer to the sixth hour they don't mean 6am or 6pm but midday; solar noon. The use of temporal hours went on into the middle ages.

31 - Many old UK churches have sundials inscribed outside of their south facing doorways. They tend to be half round with a simple pin in the centre, although the pins rarely survive. These old 'Mass' dials were, as the name suggests, a simple way of showing the times of the daily offices of prayer, communion etc,.
They are often very difficult to see due to the weathering of the years. Some will have been obscured by the later building on of porches.


	Kent Sundials - Sundials designed and made in England

	Sundial Facts
	4th July 2011 - North comes in 3 'varieties'. True North (also called solar North), compass North and Grid north (as the grids on an ordanance survey map). Sundials must be set to true north to be accurate. An OS map will often tell you on the boarder what the difference is between compass north and true north where you are, good enough for setting a sundial. My information page tells you how to find true north. 28th May 2011 - Zenith - often used to describe the moment at which the sun reaches its highest point in the day (noon) but in its pure meaning Zenith is the point when the sun is directly over head, an occurrence only possible in the tropics. ( Russell Crowe uses the term in Master and Commander' as he gives a sextant class to the midshipman) 7th May 2011 - A pole place vertically into the ground will always cast a shadow in the UK. Even on midsummers day, 21st June, the sun will not be directly overhead at noon so the pole will still cast a small shadow. To enjoy 2 days in the year when a vertical pole would cast no shadow at noon you have to live between the tropics of capricorn and cancer. 17 - Sunset and Sunrise - obvious really, but the Sun rises the same time in hours before noon as it sets after it. So if sunset is at 4.30pm, which is 4 and a half hours after noon, it will rise at 7.30am, 4 and a half hours before noon. 16 - New grange is a neolithic passage tomb in Ireland, about 5000 years old. On the morning of the winter solstice (the shortest day) the Sun rises in an alignment with the passage into the tomb and strikes the back wall of the main cruciform shaped chamber. Why choose the Winter Solstice? why not summer or equinox? Maybe after the hard dark days of winter it was important to recognize that days were getting longer again? Very 'Indiana Jones' and well worth a visit. 14 - Local Noon is when the sun is directly overhead where you are. Where I live in Ashford Kent it is local noon about 4 minutes before it is noon by my watch (Greenwich Mean time) because Ashford is about 1 degree East of Greenwich. If a football pitch lies east to west the local time difference from one goal to the other will be about a quarter of a second, this is why we all live in time zones rather than use local time. 12 - We have seasons because the earths axis tilts at 23.5 degrees. As we go around the sun we tilt toward it, giving us summer and 6months later away, giving us winter. If the earth was not tilted on its axis we wouldn't have seasons. 36 - Your watch can act as a pretty good compass. Stand with your watch face horizontal and move your wrist until the hour hand faces the Sun. Due south is the direction being pointed at by the 12 o'clock mark. 35 - The Sun is in the same place every day at the same time. When you view the sun at a fixed point from your home or any other consistent point it will always be at the same position. In the summer it will be higher in the sky and in the winter much lower, but always in the same place. The sun will be below the horizon early and late on winter days so not visable but will be in the same place in the summer but above the horizon because the northern hemisphere tilts more toward the sun in the summer. 34 - Mass produced sundials are made to suit a general latitude and can therefore never be accurate as a sundial must be made to suit the latitude it is to be located at. In the past many were made in the industrial midlands so they were set at about 52 degrees north, not too bad for most UK sites. Today many come from China, so the latitude they are made to suit could be ?!??!! Is there anything more disappointing than a truly inaccurate sundial? 33 - the Babylonian hour - You may have heard this term used on certain sundials, it means the hours since the sun has risen and can be found on many old sundials. If the sun rose at 4am and it is midday the Babylonian hour is 8. 32 - 12 'hour' days - In the ancient days of Greece and Rome the days were divided into 12 'temporal' hours. As days were determined by sunrise and sunset the hours varied in length depending on the season. Around the equinoxes you would of course get around 60 minutes in each temporal hour but in winter each hour could be as short as 40 minutes. Therefore, in ancient texts if they refer to the sixth hour they don't mean 6am or 6pm but midday; solar noon. The use of temporal hours went on into the middle ages. 31 - Many old UK churches have sundials inscribed outside of their south facing doorways. They tend to be half round with a simple pin in the centre, although the pins rarely survive. These old 'Mass' dials were, as the name suggests, a simple way of showing the times of the daily offices of prayer, communion etc,. They are often very difficult to see due to the weathering of the years. Some will have been obscured by the later building on of porches.