\begin{definition}[Definition:Sextant]
A '''sextant''' is a device for measuring the celestial altitude of a celestial body.
It consists of a telescope and a system of adjustable reflectors for presenting the image of the celestial body to the eye so as to be next to an image of the horizon.
The resulting reading on the scale of the '''sextant''' gives an indication of the altitude of the body.
\end{definition}