Stellarscopes are used to bottle the light of stars. Each star has a different color of light. It is illegal to bottle light from the unmapped stars. They appear in the form of something similar to an upside down spyglass. It is usually used by a pair of people who stand quite close together, as one cradles it and the other isolates the star using the machines knobs.
Sophie was assigned a star-mapping project in her Universe class by Sir Astin. She had to use a stellarscope to bottle the light of the 6 stars on the list and then bottle the light of a seventh, based on the pattern. She went with Dex to Moonglade, a beach with few visitors, to do their Universe homework. They set up a stellarscope to bottle the light of the stars. After Dex finished his assignment, Sophie bottled the light of the first 6 stars. Her pattern was metals, but when she plotted the stars on a map, the stars formed two lines pointing to Elementine, an unmapped star. The stellarscope got very hot after they bottled the light because the light from Elementine was Quintessence, light in its truest form.