There are many watches on the market. Even a keychain pocket watch consist of a stylus that indicates the direction of the North-South.
Every keychain pocket watch has a special system. This enables the classification of sundials and more with vertical quadrant into two types:
- To mark the hour lines in this quadrant must also make use of plane trigonometry.
- In practice, used as a clock reference template horizontal dial.
As a curiosity, they can be considered portable watches. These models can participate in the two characteristics, horizontal and vertical meridian, and which must, of course, oriented so that the vertical wall facing toward the south. The Gnomon marker of hours is a thread that serves to maintain the angle of 90 ° between the two quadrants. Thus, the same thread form takes place with the horizontal plane an angle equal to the latitude of the place. Therefore the vertical angle equals the co-latitude of the place.
Vertical Declining Quadrant
As old and traditional watches, all models have a straight line containing the Gnomon and it has a north-south forming an angle with the horizontal that equals to the latitude. In the vertical declining, keychain pocket watch have a gnomon that is exactly parallel containing the dial of the watch. The hour lines are parallel to the direction of Gnomon. In these cases it is the Gnomon that gets separated from the wall and connected to it through very fine needles, so that the shadow can be defined on the quadrant.
We can make a comparison between a keychain pocket watch performance and the functionality of a wall watch. If a clock equatorial dial must be built into a wall of a building, for example, it is difficult for the wall to be oriented exactly toward the south, which would be for simplicity in construction, as recommended. In general, then, these watches are vertical decline. The basic idea is that the wall is facing to the south as possible.
Starting from the basic types of models you can find keychain pocket watch models of many different shapes and positions with respect to their quadrants. We can easily imagine watches spherical, cylindrical-shaped dish, etc. The important thing about all these different clocks presentation is based on the fact that our planet rotates at 15 º time and that we call it an hour. We know that at noon the shadow of a gnomon on a horizontal plane is the smallest of the day. And that noon is reached simultaneously at all points of the same meridian. a
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