and the tabula orbis signorum, directly hinged to it above. The angle between these two pieces is defined by the basilica, a solid stand piece, which is used to either set the draft angle at 0 degrees (Where the basilica is removed) or 23.5 degrees, representing the off-set of the axis of rotation of the Earth. Whether or not the basilica is included depends on the point of measurement either below or above the tropical latitudinal lines. Inscribed on the tabula equinoctialis along, although separate from, the outer perimeter of the bottom disk is a 24-hour circle, which is used to measure the angle between the longitudinal line facing the poles, and the line to the object being measured. Lastly, the upper frame is made up of the crista, the semis and the perpendiculum. The base of the crista is joined to another free-spinning disk directly above the tabula orbis signorum. Similarly, on the outer edge of the tabula orbis signorum is a zodiacal calendar and degree scale, with each of the 12 signs divided amongst it. This scale measures the zodiacal sector of the sky the object being measured is in. The crista itself is a circular piece that corresponds with the meridian of the celestial sphere, which has four quadrants inscribed along the edges, each starting at 0 degrees along the horizontal, and 90 degrees along the vertical. Adjacent, and locked with the crista at 23.5 degrees angle is the semis, which is a half-circle composed of two quadrants starting at 0 degrees along the vertical (relative to 23.5-degree placement) and 90 degrees at the horizontal. Finally, the last major component is the perpendicular, a free-hanging pendulum which measures the angle between the radial line of the Earth and the measured object using the semis. Parts and configurations The base of the instrument represents the horizon and is built on a hinge and a part known as the stylus holds the instrument up to the viewer's complementary latitude. This represents the celestial equator and the angle varies depending on where the view is located on Earth. The several plates and circles that make up the upper portion of the instrument represent the celestial sphere. These parts are built on top of the base and above the basilica, which rotates on a pin to represent the axis of the Earth. The zodiac calendar is inscribed on the tabula orbis