Callisto, also known as Jupiter's moon Callisto (pronounced/k əˈ l ɪ sto ʊ, Greek: Καλλιστώ), is a satellite that orbits Jupiter and was first discovered by Galileo Galilei in 1610. Europa is the third largest moon in the solar system and the second largest moon of Jupiter, second only to Ganymede.

Built by artist Joseph von Utzschner in the first half of the 19th century, this instrument is an observational astronomical device used to determine the height of celestial bodies above the horizon. It consists of a frame limited by two radii, an arc with a scale, an observation telescope, and a mirror system. It is used to determine the position of celestial bodies by using a mirror system that produces a reflection image of the observed object parallel to the horizon in the observer's field of view. In order to observe the position of the sun, a filter is used to limit the amount of light reaching the observer's eyes. The instrument is currently housed in the Jagiellonian University Museum in Munich, Germany.

An observational astronomical instrument of the first half of the 19th century used to determine the height of a celestial body above the horizon. It consists of a frame limited by two radii and a graduated arc, an observation telescope and a mirror system. The 1/5 arc is the fifth part of the circle, hence the name, similar to the quadrants, 1/6, and 1/8 (based on the fourth, sixth, and eighth parts of the circle, respectively). It is currently housed in the Jagiellon University Museum in Munich, Germany.