Rubu Board Making Guide

First used in the Islamic world, the quadrant can, in a sense, be considered the ancestor of computers. With the help of this inexpensive and practical tool, the Sun's horizon height can be measured to accurately determine prayer and fasting times, trigonometric functions of angles can be solved, and various arithmetic operations can be easily performed.

The mathematics of the rub'-ul mukantarat on the front face of the quadrant – used for solar observations – is essentially the same as that of the astrolabe. In short, it can be described as a quadrupled version of the astrolabe. Western astronomers did not use the quadrant, preferring the astrolabe instead.

Especially because they allowed for easy determination of prayer times, quadrants were among the essential tools of "muvakkithanes" (time-keeping houses). This instrument, which was used in the Ottoman Empire until the early 20th century, later became obsolete and forgotten in the face of the vast possibilities offered by modern technology.