In addition to the primary and secondary mirrors, NAYUTA has a third mirror that serves the purpose of horizontally reflecting the light from the secondary mirror.

In technical terms, the point where light from the secondary mirror converges is called the Cassegrain focus, and the point to where light from the third mirror is shifted horizontally is called the Nasmyth focus. Each of these foci has its own characteristics.

A more detailed description of these characteristics is provided in the next section, but it is important to note that these three foci are used accordingly to conduct various observation activities, and that the third mirror plays a critical role in ensuring efficiency.