Abstract: An ultraviolet risk indicator instrument comprising a dial and a shadow projection device on it, the dial having colored areas that indicate different UV risks, defined by lines of declination (solstices and equinoxes) and solar hour lines calculated based on the transformation of the Hour Coordinates of the Sun (Hour Angle and Declination) in a 3D Cartesian Coordinate System, whose origin is the tip of the shadow projection device (being a polar style parallel to the rotation axis of the Earth, or a straight style perpendicular to the dial plane) using matrix calculations to produce the necessary rotations of the system, taking into account the latitude of the place, the declination and inclination of the dial. The style may be a rod or a triangular shape.

Abstract: An ultraviolet risk indicator instrument comprising a dial and a shadow projection device on it, the dial having colored areas that indicate different UV risks, defined by lines of declination (solstices and equinoxes) and solar hour lines calculated based on the transformation of the Hour Coordinates of the Sun (Hour Angle and Declination) in a 3D Cartesian Coordinate System, whose origin is the tip of the shadow projection device (being a polar style parallel to the rotation axis of the Earth, or a straight style perpendicular to the dial plane) using matrix calculations to produce the necessary rotations of the system, taking into account the latitude of the place, the declination and inclination of the dial. The style may be a rod or a triangular shape.