זמן ומדידה

The Planispheric Astrolabe as an Observer-Frame Projection Engine

תוכן האובייקטים עצמם כתוב באנגלית ועדיין לא תורגם.

תקופה ומקור

Hellenistic origin, developed in the Islamic world from the eighth century and in Latin Europe thereafter

מה הוא נבנה לעשות

To answer questions about altitude, azimuth, sidereal and solar time, rising, setting, meridian transit, seasonal hours and direction by superposing two coordinate systems of the celestial sphere on one plane.

כיצד המנגנון פועל

Stereographic projection maps celestial circles to circles or lines and preserves angles. A movable rete represents the rotating stellar sphere and ecliptic; a latitude-specific tympan represents the observer’s horizon, altitude circles and azimuth circles. Their relative rotation is the computation.

קלט

An observed altitude, or a date and time, set by rotating the rete against the tympan.

טרנספורמציה

Stereographic projection of two celestial frames onto one plane, composed by the relative rotation of the two plates.

פלט

The remaining unknowns of the same configuration, read directly off the graduated limb and the tympan’s circles.

מה מבוסס בראיות

מבוסס: הממצא או התיעוד נושאים זאת במישרין.

מה הוא מדגים

That a transformation between reference frames can be built into a shape, so that solving for one quantity is a matter of alignment rather than calculation.

כל המנגנונים