Exploring Sundials - Revision history

DT Online at 09:40, 1 March 2017

2017-03-01T09:40:23Z

← Older revision		Revision as of 09:40, 1 March 2017
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	=====Introduction=====		=====Introduction=====

	A [~~https~~://en.wikipedia.org/wiki/Sundial '''Sundial'''] of sorts can quite easily be made by pushing a pencil through the centre of a paper plate and placing it in a sunny position such that the pencil casts a shadow.		A [http://en.wikipedia.org/wiki/Sundial '''Sundial'''] of sorts can quite easily be made by pushing a pencil through the centre of a paper plate and placing it in a sunny position such that the pencil casts a shadow.


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	It can be imagined that a '''[[Sundials and Gnomons\|Sundial]]''' designed to sit at the North Pole would be identical to one placed at the centre of the Earth on the [~~https~~://en.wikipedia.org/wiki/Equator '''Equator'''], if that were possible, and so '''[[Sundials and Gnomons\|Sundial]]''' with equally spaced divisions as shown are known as '''Equatorial Sundials'''. These can be regarded as ‘master sundials’ from which designs for others may be generated.		It can be imagined that a '''[[Sundials and Gnomons\|Sundial]]''' designed to sit at the North Pole would be identical to one placed at the centre of the Earth on the [http://en.wikipedia.org/wiki/Equator '''Equator'''], if that were possible, and so '''[[Sundials and Gnomons\|Sundial]]''' with equally spaced divisions as shown are known as '''Equatorial Sundials'''. These can be regarded as ‘master sundials’ from which designs for others may be generated.
	[[File:SundialScaleLabelled.png \|300px\|right\|Horizontal Sundial]]		[[File:SundialScaleLabelled.png \|300px\|right\|Horizontal Sundial]]

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	As is the case with other '''Sundials''', the '''[[Sundials and Gnomons\|Gnomon]]''' remains pointing North and at an angle equal to the '''[[Latitude]]''' of where the '''Sundial''' is to be positioned. Note that the angles between the '''''hour lines''''' increase as the Sun's shadow deviates away from Noon during both morning and afternoon. This gives rise to the familiar splayed lines on a modern '''Horizontal Sundial''' and as seen on the face of the '''[[:Category:Ancient Egypt\|Ancient Egyptian]]''' sundial discovered in the [~~https~~://en.wikipedia.org/wiki/Valley_of_the_Kings '''Valley of the Kings'''] around 1500 BC.		As is the case with other '''Sundials''', the '''[[Sundials and Gnomons\|Gnomon]]''' remains pointing North and at an angle equal to the '''[[Latitude]]''' of where the '''Sundial''' is to be positioned. Note that the angles between the '''''hour lines''''' increase as the Sun's shadow deviates away from Noon during both morning and afternoon. This gives rise to the familiar splayed lines on a modern '''Horizontal Sundial''' and as seen on the face of the '''[[:Category:Ancient Egypt\|Ancient Egyptian]]''' sundial discovered in the [http://en.wikipedia.org/wiki/Valley_of_the_Kings '''Valley of the Kings'''] around 1500 BC.
	[[File:Sundial-egypt.png\|200px\|right\|Horizontal Sundial]]		[[File:Sundial-egypt.png\|200px\|right\|Horizontal Sundial]]

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	The results will show that '''Horizontal Sundials''' work best at higher '''[[Latitude\|Latitudes]]''' rather than near the [~~https~~://en.wikipedia.org/wiki/Equator '''Equator'''].		The results will show that '''Horizontal Sundials''' work best at higher '''[[Latitude\|Latitudes]]''' rather than near the [http://en.wikipedia.org/wiki/Equator '''Equator'''].


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	Ideally, the 'dial' of a '''Vertical Sundial''' should be fixed to a South-facing wall or surface. In this situation the '''[[Sundials and Gnomons\|Gnomon]]''' is located in a plane at right angles to the 'dial' and will cast a vertical shadow at Noon. If placed on a wall which is not South-facing ''(e.g. S.E. or S.W.)'' then the '''[[Sundials and Gnomons\|Gnomon]]''' will need to be angled to the 'dial' such that the shadow cast at Noon remains vertical and is said to be [~~https~~://en.wikipedia.org/wiki/Declination '''Declined'''] East or West as appropriate.		Ideally, the 'dial' of a '''Vertical Sundial''' should be fixed to a South-facing wall or surface. In this situation the '''[[Sundials and Gnomons\|Gnomon]]''' is located in a plane at right angles to the 'dial' and will cast a vertical shadow at Noon. If placed on a wall which is not South-facing ''(e.g. S.E. or S.W.)'' then the '''[[Sundials and Gnomons\|Gnomon]]''' will need to be angled to the 'dial' such that the shadow cast at Noon remains vertical and is said to be [http://en.wikipedia.org/wiki/Declination '''Declined'''] East or West as appropriate.


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	The results will show that '''Vertical Sundials''' work well if nearer to the [~~https~~://en.wikipedia.org/wiki/Equator '''Equator'''] than the North Pole.		The results will show that '''Vertical Sundials''' work well if nearer to the [http://en.wikipedia.org/wiki/Equator '''Equator'''] than the North Pole.

	----		----

DT Online at 22:57, 7 November 2016

2016-11-07T22:57:28Z

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	'''<big>Horizontal dial shadow angle θ = Arctan (Sin Latitude(L) x Tan H)</big>'''		'''<big>Horizontal dial shadow angle θ = Arctan (Sin Latitude(L) x Tan H)</big>'''

	[[File:~~A.-Worsall-Stainless-dial~~.png\|150px\|right\|Horizontal Sundial]]		[[File:HorizontalSundialEG.png\|150px\|right\|Horizontal Sundial]]
	Where:		Where:
	* θ = the '''hour angle''' ''(i.e. the deviation away from the North-facing Noon line)'';		* θ = the '''hour angle''' ''(i.e. the deviation away from the North-facing Noon line)'';

DT Online at 16:28, 24 October 2016

2016-10-24T16:28:42Z

← Older revision		Revision as of 16:28, 24 October 2016
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	----		----
	<span style="color: green">'''Note:'''		<span style="color: green">'''Note:'''
	~~A [https://docs.google.com/spreadsheets/d/1rdxuEJJgqAk4VXVkqeqxUDnfm2TNRz9pe9VwKzB6tLI/edit?usp=sharing~~ '''DT Online ~~Tool~~'''~~] is~~ available ~~[https://docs.google.com/spreadsheets/d/1rdxuEJJgqAk4VXVkqeqxUDnfm2TNRz9pe9VwKzB6tLI/edit?usp=sharing~~ '''~~here~~'''] which ~~completes the calculation of the angle of~~ each '''''hour line''''' for any given '''[[Latitude]]''' which is input.		To check your '''Hour Lines''', '''[[Sundial Design Tools\|DT Online Design Tools]]''' are available '''[[Sundial Design Tools\|HERE]]''' which calculate each '''''hour line''''' for any given '''[[Latitude]]''' which is input and optionally print-out a '''[[Template]]''' of the resulting 'Dial Plate'.
	</span>		</span>
	----		----

DT Online at 12:22, 20 October 2016

2016-10-20T12:22:34Z

← Older revision		Revision as of 12:22, 20 October 2016
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	The distance between the parallel '''hour lines''' is determined only by the height of the '''[[Sundials and Gnomons\|Gnomon]]''' and not '''[[Latitude]]~~''' as with other '''Sundials~~'''.		The distance between the parallel '''hour lines''' is determined only by the height of the '''[[Sundials and Gnomons\|Gnomon]]''' and is not affected by '''[[Latitude]]'''.

DT Online: Added Polar Dial calibration Image

2016-10-20T12:19:22Z

Added Polar Dial calibration Image

← Older revision		Revision as of 12:19, 20 October 2016
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	[[File:VerticalDial2.png\|150px\|right\|~~Horizontal~~ Sundial]]		[[File:VerticalDial2.png\|150px\|right\|Vertical Sundial]]
	=====Vertical Sundial=====		=====Vertical Sundial=====

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	----		----

	[[File:PolarDial.png\|300px\|right\|~~Horizontal~~ Sundial]]		[[File:PolarDial.png\|300px\|right\|Polar Sundial]]
	=====Polar Sundial=====		=====Polar Sundial=====

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	[[File:~~PolarSundial2~~.png\|~~300px~~\|right\|~~Horizontal~~ Sundial~~\|link=http://www.geograph.org.uk/photo/1467060~~]]		[[File:PolarSundial3.png\|400px\|right\|Polar Sundial calibration]]
	These are known as '''Polar Sundials''': the 'dial plate' is fixed parallel with the Earth's axis; the '''[[Sundials and Gnomons\|Gnomon]]''' is parallel to the 'dial plate'; and the '''hour lines''' are parallel to each other along the length of the 'dial plate'. Typically the '''[[Sundials and Gnomons\|Gnomon]]''' is formed by the edge of a rectangular plate fixed across the centre of the 'dial plate' at the Noon position.		These are known as '''Polar Sundials''': the 'dial plate' is fixed at an angle parallel with the Earth's axis; the '''[[Sundials and Gnomons\|Gnomon]]''' is parallel to the 'dial plate'; and the '''hour lines''' are parallel to each other along the length of the 'dial plate'. Typically the '''[[Sundials and Gnomons\|Gnomon]]''' is formed by the edge of a rectangular plate fixed across the centre of the 'dial plate' at the Noon position.


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			[[File:PolarSundial2.png\|250px\|right\|Polar Sundial\|link=http://www.geograph.org.uk/photo/1467060]]
	The distance of other '''hour lines''' from the '''[[Sundials and Gnomons\|Gnomon]]''' may be calculated using '''[[Trigonometry]]''' as follows:		The distance of other '''hour lines''' from the '''[[Sundials and Gnomons\|Gnomon]]''' may be calculated using '''[[Trigonometry]]''' as follows:

DT Online at 19:41, 19 October 2016

2016-10-19T19:41:53Z

← Older revision		Revision as of 19:41, 19 October 2016
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	As is the case with other '''Sundials''', the '''[[Sundials and Gnomons\|Gnomon]]''' remains pointing North and at an angle equal to the '''[[Latitude]]''' of where the '''Sundial''' is to be positioned. Note that the angles between the '''''hour lines''''' increase as the Sun's shadow deviates away from Noon during both morning and afternoon. This gives rise to the familiar splayed lines on a modern '''Horizontal Sundial''' and as seen on the face of the '''[[:Category:Ancient Egypt\|Ancient Egyptian]]''' sundial discovered in the [https://en.wikipedia.org/wiki/Valley_of_the_Kings '''Valley of the Kings'''] around 1500 BC.		As is the case with other '''Sundials''', the '''[[Sundials and Gnomons\|Gnomon]]''' remains pointing North and at an angle equal to the '''[[Latitude]]''' of where the '''Sundial''' is to be positioned. Note that the angles between the '''''hour lines''''' increase as the Sun's shadow deviates away from Noon during both morning and afternoon. This gives rise to the familiar splayed lines on a modern '''Horizontal Sundial''' and as seen on the face of the '''[[:Category:Ancient Egypt\|Ancient Egyptian]]''' sundial discovered in the [https://en.wikipedia.org/wiki/Valley_of_the_Kings '''Valley of the Kings'''] around 1500 BC.
			[[File:Sundial-egypt.png\|200px\|right\|Horizontal Sundial]]


	~~[[File:Sundial-egypt.png\|200px\|right\|Horizontal Sundial]]~~
	The calculation of the angles for the '''''hour lines''''' requires some quite advanced '''[[Trigonometry]]''' as follows:		The calculation of the angles for the '''''hour lines''''' requires some quite advanced '''[[Trigonometry]]''' as follows:

	'''<big>Horizontal dial shadow angle θ = Arctan (Sin Latitude(L) x Tan H)</big>'''		'''<big>Horizontal dial shadow angle θ = Arctan (Sin Latitude(L) x Tan H)</big>'''

			[[File:A.-Worsall-Stainless-dial.png\|150px\|right\|Horizontal Sundial]]
	Where:		Where:
	* θ = the '''hour angle''' ''(i.e. the deviation away from the North-facing Noon line)'';		* θ = the '''hour angle''' ''(i.e. the deviation away from the North-facing Noon line)'';

DT Online at 12:09, 19 October 2016

2016-10-19T12:09:04Z

← Older revision		Revision as of 12:09, 19 October 2016
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	=====Polar Sundial=====		=====Polar Sundial=====

	If a strip,of material is placed across the end of a '''Horizontal Sundial''' such that the Sun's shadows are able to project on to it and tilted at the '''[[Latitude]]''' angle, it will be seen that the shadows generate parallel lines on the tilted plate. As the distance to the 6am and 6pm '''hour lines''' approach infinity, the time that can be indicated by the dial is limited to the practical width of the dial plate ''(or the curve of the 'dial plate' in designs adopting this solution)''.		If a strip,of material is placed across the end of a '''Horizontal Sundial''' such that the Sun's shadows are able to project on to it, and tilted at the '''[[Latitude]]''' angle, it will be seen that the shadows generate parallel lines on the tilted plate. As the distance to the 6am and 6pm '''hour lines''' approach infinity ''(i.e. when the Sun's rays are parallel to the 'dial plate')'', the time that can be indicated by the dial is limited to the practical width of the 'dial plate' ''(or the curve of the 'dial plate' in designs adopting this solution)''.


	[[File:PolarSundial2.png\|300px\|right\|Horizontal Sundial\|link=http://www.geograph.org.uk/photo/1467060]]		[[File:PolarSundial2.png\|300px\|right\|Horizontal Sundial\|link=http://www.geograph.org.uk/photo/1467060]]
	These are known as '''Polar Sundials''': the 'dial plate' is fixed parallel with the Earth's axis; the '''[[Sundials and Gnomons\|Gnomon]]''' is parallel to the 'dial plate'; and the '''hour lines''' are parallel to each other along the length of the 'dial plate'. Typically the '''[[Sundials and Gnomons\|Gnomon]]''' is formed by the edge of a rectangular plate fixed across the centre of the dial plate at the Noon position.		These are known as '''Polar Sundials''': the 'dial plate' is fixed parallel with the Earth's axis; the '''[[Sundials and Gnomons\|Gnomon]]''' is parallel to the 'dial plate'; and the '''hour lines''' are parallel to each other along the length of the 'dial plate'. Typically the '''[[Sundials and Gnomons\|Gnomon]]''' is formed by the edge of a rectangular plate fixed across the centre of the 'dial plate' at the Noon position.

DT Online at 11:44, 19 October 2016

2016-10-19T11:44:55Z

← Older revision		Revision as of 11:44, 19 October 2016
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	[[File:PolarSundial2.png\|300px\|right\|Horizontal Sundial\|link=http://www.geograph.org.uk/photo/~~516403~~]]		[[File:PolarSundial2.png\|300px\|right\|Horizontal Sundial\|link=http://www.geograph.org.uk/photo/1467060]]
	These are known as '''Polar Sundials''': the 'dial plate' is fixed parallel with the Earth's axis; the '''[[Sundials and Gnomons\|Gnomon]]''' is parallel to the 'dial plate'; and the '''hour lines''' are parallel to each other along the length of the 'dial plate'. Typically the '''[[Sundials and Gnomons\|Gnomon]]''' is formed by the edge of a rectangular plate fixed across the centre of the dial plate at the Noon position.		These are known as '''Polar Sundials''': the 'dial plate' is fixed parallel with the Earth's axis; the '''[[Sundials and Gnomons\|Gnomon]]''' is parallel to the 'dial plate'; and the '''hour lines''' are parallel to each other along the length of the 'dial plate'. Typically the '''[[Sundials and Gnomons\|Gnomon]]''' is formed by the edge of a rectangular plate fixed across the centre of the dial plate at the Noon position.

DT Online at 11:42, 19 October 2016

2016-10-19T11:42:20Z

← Older revision		Revision as of 11:42, 19 October 2016
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	[[File:PolarSundial2.png\|300px\|right\|Horizontal Sundial]]		[[File:PolarSundial2.png\|300px\|right\|Horizontal Sundial\|link=http://www.geograph.org.uk/photo/516403]]
	These are known as '''Polar Sundials''': the 'dial plate' is fixed parallel with the Earth's axis; the '''[[Sundials and Gnomons\|Gnomon]]''' is parallel to the 'dial plate'; and the '''hour lines''' are parallel to each other along the length of the 'dial plate'. Typically the '''[[Sundials and Gnomons\|Gnomon]]''' is formed by the edge of a rectangular plate fixed across the centre of the dial plate at the Noon position.		These are known as '''Polar Sundials''': the 'dial plate' is fixed parallel with the Earth's axis; the '''[[Sundials and Gnomons\|Gnomon]]''' is parallel to the 'dial plate'; and the '''hour lines''' are parallel to each other along the length of the 'dial plate'. Typically the '''[[Sundials and Gnomons\|Gnomon]]''' is formed by the edge of a rectangular plate fixed across the centre of the dial plate at the Noon position.

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	The ring is known as the '''Equatorial Ring''' and the hour lines are spaced equally around it at 15<small><sup>0</sup></small>. intervals.		The ring is known as the '''Equatorial Ring''' and the '''hour lines''' are spaced equally around it at 15<small><sup>0</sup></small>. intervals.

DT Online: Added Polar and Armillary Sundials

2016-10-19T11:10:57Z

Added Polar and Armillary Sundials

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-[[File:PaperPlateDial.png|175px|right]]
+[[File:PaperPlateDial.png|225px|right]]
 __TOC__
@@ Line 32: / Line 32: @@
 [[File:Sundial-egypt.png|200px|right|Horizontal Sundial]]
 The calculation of the angles for the '''''hour lines''''' requires some quite advanced '''[[Trigonometry]]''' as follows:
 '''
-<big>Horizontal dial shadow angle θ = Arctan (Sin Latitude(L) x Tan H)</big>'''
+'''<big>Horizontal dial shadow angle θ = Arctan (Sin Latitude(L) x Tan H)</big>'''
 Where:
@@ Line 55: / Line 55: @@
 The calculation of the angles for the '''''hour lines''''' requires similar advanced '''[[Trigonometry]]''' as for '''Horizontal Sundials''':
-'''<big>Horizontal dial shadow angle θ = Arctan (Cos Latitude(L) x Tan H)</big>'''[[File:VerticalSunDial3.png|200px|right|Vertical Sundial]]
+'''<big>Vertical dial shadow angle θ = Arctan (Cos Latitude(L) x Tan H)</big>'''[[File:VerticalSunDial3.png|200px|right|Vertical Sundial]]
 Where the variables are the same as given above for the '''Horizontal Sundial''' but note that it is the '''[[Trigonometry|Cosine]]''' of '''[[Latitude]]''' which is used rather than the '''[[Trigonometry|Sine]]'''.
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 The results will show that '''Vertical Sundials''' work well if nearer to the [https://en.wikipedia.org/wiki/Equator '''Equator'''] than the North Pole.
 ----
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 </span>
 ----
 {{Sundials Buyers Guide}}
 [[Category:Sundials]]