Editing Sundial (section)

==Unusual sundials==

===Benoy dial===
[[File:Benoy sun clock.jpg|upright|thumb|170px|Benoy Sun Clock showing 6:00 p.m.]]
The Benoy dial was invented by Walter Gordon Benoy of [[Collingham, Nottinghamshire]], England. Whereas a gnomon casts a sheet of shadow, his invention creates an equivalent sheet of light by allowing the Sun's rays through a thin slit, reflecting them from a long, slim mirror (usually half-cylindrical), or focusing them through a [[cylindrical lens]]. Examples of Benoy dials can be found in the United Kingdom at:<ref name="BSSRegister">List correct as of British Sundial Register 2000. {{cite web |title=The Sundial Register |url=http://www.sundialsoc.org.uk/register.htm |url-status=dead |archive-url=https://web.archive.org/web/20070717073638/http://www.sundialsoc.org.uk/register.htm |archive-date=2007-07-17 |access-date=2008-01-05 |website=British Sundial Society}}</ref>
*Carnfunnock Country Park, [[County Antrim]], Northern Ireland
*Upton Hall, [[British Horological Institute]], [[Newark-on-Trent]], Nottinghamshire
*Within the collections of St Edmundsbury Heritage Service, [[Bury St Edmunds]]<ref>{{cite web|last=St. Edmundsbury |first=Borough Council |title=Telling the story of time measurement |url=http://www.stedmundsbury.gov.uk/sebc/visit/Telling-the-Story-of-Time-Measurement.cfm |access-date=2008-01-05 |url-status=dead |archive-url=https://web.archive.org/web/20071224121416/http://www.stedmundsbury.gov.uk/sebc/visit/Telling-the-Story-of-Time-Measurement.cfm |archive-date=December 24, 2007 }}</ref>
*[[Longleat]], Wiltshire
* [[Jodrell Bank]] Science Centre
* [[Birmingham Botanical Gardens (United Kingdom)|Birmingham Botanical Gardens]]
* [[Science Museum, London]] (inventory number 1975-318)

===Bifilar sundial===
[[File:Stainless steel bifilar sundial (dial).jpg|thumb|Stainless steel bifilar sundial in Italy]]
{{main|Bifilar sundial}}
Invented by the German mathematician Hugo Michnik in 1922, the [[bifilar sundial]] has two non-intersecting threads parallel to the dial. Usually the second thread is [[orthogonal]] to the first.<ref name="1922AN....217...81M">{{cite journal|last=Michnik|first=H|date=1922|title=Title: Theorie einer Bifilar-Sonnenuhr|journal=Astronomische Nachrichten |volume=217 |issue=5190|pages=81–90|language=de|url=http://articles.adsabs.harvard.edu//full/1922AN....217...81M/0000045.000.html|access-date=17 December 2013|bibcode=1922AN....217...81M|doi=10.1002/asna.19222170602|archive-date=17 December 2013|archive-url=https://web.archive.org/web/20131217221544/http://articles.adsabs.harvard.edu//full/1922AN....217...81M/0000045.000.html|url-status=live}}</ref>
The intersection of the two threads' shadows gives the local solar time.

===Digital sundial===
{{Main|Digital sundial}}
A digital sundial indicates the current time with numerals formed by the sunlight striking it. Sundials of this type are installed in the [[Deutsches Museum]] in Munich and in the Sundial Park in [[Genk]] (Belgium), and a small version is available commercially. There is a patent for this type of sundial.<ref>{{Cite web |url=http://www.digitalsundial.com/patent.html |title=Digital sundial |access-date=2013-07-12 |archive-date=2021-01-25 |archive-url=https://web.archive.org/web/20210125011217/http://www.digitalsundial.com/patent.html |url-status=live }}</ref>

===Globe dial===
The globe dial is a sphere aligned with the Earth's rotational axis, and equipped with a spherical vane.<ref>{{harvp|Rohr|1996|pp=114–115}}</ref> Similar to sundials with a fixed axial style, a globe dial determines the time from the Sun's azimuthal angle in its apparent rotation about the earth. This angle can be determined by rotating the vane to give the smallest shadow.

===Noon marks===
{{Main|Noon mark}}
[[File:Greenwich Royal Observatory Noon Mark.jpg|thumb|170px|[[Noon mark]] from the [[Greenwich Royal Observatory]]. The analemma is the narrow figure-8 shape, which plots the [[equation of time]] (in degrees, not time, 1°=4 minutes) versus the altitude of the Sun at noon at the sundial's location. The altitude is measured vertically, the equation of time horizontally.]]

The simplest sundials do not give the hours, but rather note the exact moment of 12:00&nbsp;noon.<ref>{{harvp|Waugh|1973| pp=18–28}}</ref> In centuries past, such dials were used to set mechanical clocks, which were sometimes so inaccurate as to lose or gain significant time in a single day. The simplest noon-marks have a shadow that passes a mark. Then, an almanac can translate from local solar time and date to civil time. The civil time is used to set the clock. Some noon-marks include a figure-eight that embodies the [[equation of time]], so that no almanac is needed.

In some U.S. colonial-era houses, a noon-mark might be carved into a floor or windowsill.<ref>{{harvp|Mayall|Mayall|1994|p=26}}</ref> Such marks indicate local noon, and provide a simple and accurate time reference for households to set their clocks. Some Asian countries<!-- Date and location needed--> had post offices set their clocks from a precision noon-mark. These in turn provided the times for the rest of the society. The typical noon-mark sundial was a lens set above an [[analemma]]tic plate. The plate has an engraved figure-eight shape, which corresponds to the [[equation of time]] (described above) versus the solar declination. When the edge of the Sun's image touches the part of the shape for the current month, this indicates that it is 12:00&nbsp;noon.

===Sundial cannon===
{{main|Sundial cannon}}
A [[sundial cannon]], sometimes called a 'meridian cannon', is a specialized sundial that is designed to create an 'audible noonmark', by automatically igniting a quantity of gunpowder at noon. These were novelties rather than precision sundials, sometimes installed in parks in Europe mainly in the late 18th or early 19th&nbsp;centuries. They typically consist of a horizontal sundial, which has in addition to a [[gnomon]] a suitably mounted [[lens (optics)|lens]], set to focus the rays of the sun at exactly noon on the firing pan of a miniature [[cannon]] loaded with [[gunpowder]] (but no [[round shot|ball]]). To function properly the position and angle of the lens must be adjusted seasonally.{{citation needed|date=June 2013}}