a moveable, tiltable device that can be set to match any surface on a model to show angle of incidence. The angle of incidence device indicates the relative intensity of the direct beam on the surface. The device consists of a diagram of concentric rings around a shadow-casting pointer perpendicular to the diagram. Each ring represents a percent of the direct solar beam incident on the surface. The percentage varies from 100%—the ray runs straight down the pointer perpendicular to the diagram—to zero—the ray runs parallel to the diagram and misses surface. The cosine of the angle of incidence gives the percentage. A cosine of 0.9, 90%, for example, corresponds to an angle of incidence of 26.84 degrees. The radius of the ring for the angle is equal to its tangent times the height of the shadow casting pointer. A 45 degree angle of incidence would generate a cosine of about .7, 70%, for example. Since the tangent of 45 degrees is 1, the radius of the 70% ring would be equal to the height of the shadow-casting rod. Types of Heliodon Manual Tabletop Heliodon Manual Tabletop heliodons are used for sun shading analysis at any given latitude and at any time. The model support platform is mounted on a conventional table or desk. It can rotate and tilt a scaled architectural model. These heliodons are manually operated without the use of computers and provide good accuracy. The model stand, mounted on the table, is tilted for latitude and rotated to get the time of the day. For replicating the time of the year, the single light source uses a ribbon marked with months of the year and attached to the edge of the door. The device can be used in interior spaces with lamps and exterior spaces with direct sunlight for better accuracy. While using outdoors, a sundial controls the tilt and rotation of the model stand. The main advantage is its affordability and small size. The heliodon is accurate when utilized by people who are already aware of solar geometry. But not good for learning solar geometry and the basic principles of solar responsive design. Department of Architecture at the University of Hong Kong uses tabletop heliodon for the solar design of architectural scale models. The heliodon is mainly used for teaching and design purposes. Manual Sun Emulator Heliodon The manual heliodon consists of a flat table with