Tag:display=sundial

A sundial is a way of telling the local or official (standard) time using the Sun by reading the shadow on special markings.

By default, sundials tell the local time. When the standard time should be shown, it has to take into account the longitude correction and the equation of time. The geographical latitude influences the overall design of the sundial, as the angle of the gnomon (the part that casts the shadow) corresponds to the geographical latitude. The closer to equator, the less inclined is the gnomon.

The markers for time can be in Roman numerals or Arab numbers. Some sundials also show separately the standard time and the summer saving time.

A typical sundial has three main parts:

Gnomon - an object that casts a shadow on the dial.

Dial (plate or surface) - shows the time in hour increments from the shadow from the gnomon.

Base - a foundation or pedestal upon which the dial and gnomon are placed.

History

Sundials originate from ancient Egypt as a way of measure the passage of the day. They were resembling a rectangular bar with one end raised. The shadow from the raised part cast the shadow on the bar with different markings.

Later, many different sundial designs spread across Europe and Asia.

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  Byzantine sundial (reconstruction)

Its main use was to know when to pray, or for other religious intents. It was used in many cultures like the Byzantine empire, ancient Greece and others. In Roman Empire, it was used for timing in different contexts, including the military purposes.

In the modern time sundials have mainly design function, as well as they tell proper time.

Sundial and dial types

Sundial types:

Type name	Description	How it works	Typical locations	Usual materials used to make it	Image
Equatorial sundials	A sundial that has the dial plate is parallel to the equator plane and the gnomon is polar-pointing and is perpendicular to it	The shadow falls from the gnomon on the dial that is parallel to the equator	This sundial type is found mostly in gardens or public areas for people.	Metal both for the gnomon and dial, the base is from some rock or metal
Analemmatic sundials	This sundial type is designed so the person is the gnomon. It is made flat on the ground so it is easier for people to step on	Frequently, in the middle of the sundial there is a line in the shape of an 8 ("analemma"), that shows every month of the year, so you can place yourself on the right place and for the sundial to show the right time	This sundial type is mostly common in public areas or on school grounds	It is mostly made from hard materials like rocks or stone, for it to endure people stepping on it
Horizontal sundials	Horizontal sundials are the easiest sundials to make, and are the most common around the world	The plane that receives the shadow is horizontal, rather than perpendicular like equatorial sundials work. The gnomon is made in the shape of a triangle, to see the shadow the best. And the dial numbers are usually made in roman numerals	This sundial can be found in gardens or on roofs	Usually the base is made from stone or steel, and gnomon can be made from steel, glass and steel, or stone	Horizontal sundial, Albert Hall, 1740
Vertical sundials	Vertical sundials are sundials that are mounted on a wall, a pole or some other vertical surface. The shadow goes counter-clockwise rather than other sundial types	On a wall or other vertical object (towards N on the Northern hemisphere and S on the Southern hemisphere), where the gnomon is placed in the degrees on where in the world the sundial is located. In the Northern hemisphere the shadow goes counter clock wise, while the opposite is true for vertical sundials in the Southern hemisphere	Can be found on old churches, universities, or any other old building	Typically is made on a flat wall, with some ornaments on it, with the gnomon being from metal and one of the oldest ways to make a sundial	A vertical sundial
Spherical sundials (armillary sundials)	Sundials that are spherical from the outside, and are typically see through, with some metal poles.	It works cause the gnomon is aligned to the Earth's axis and casts a shadow on the dial, that tells the time	Found in gardens or public parks	Metal for gnomon, and dial. But stone or metal for the base
Cylindrical sundials	On a round pole is placed a gnomon, and then the hour lines are made on the pole, so it tells the correct time
Conical sundials	Usually a big sundial with a dial being in a conal shape, with the gnomon being in front of it
Movable gnomon sundials	These sundials have their gnomon on a rotating axis, that makes these types more versitile as they can tell the time in almost all places on earth
Altitude sundials
Sun plus Moon sundials

Dial types:

Type name	Description	How it works	Image
Polar dials
Vertical declining dials
Reclining dials
Noon mark dials

Materials

The materials used to make can vary from sundial to sundial.

For classical the gnomon is mainly from metal (mainly stainless steel to avoid corrosion) or stone. To prevent it from being damaged by the weather or vandals. In more private cases it can also be made from glass too.

The base is made from stone, concrete or paving stones, to make it stable and weatherproof.

And the dial are either carved or placed. Dials can be drawn from the gnomon as guidelines for better readability, or can be there without any movement.

How to map

Using a point, line or an area draw the sundial, and add more subtags - Description, height, website, author, and more. Adding an image can help show how the sundial looks like.