👉 The phthaleinometer is a device used in the field of astrophysics to measure the optical properties of stars. It consists of two telescopes, one for observing stars and the other for measuring their light emission. The phthaleinometer uses a series of filters called phthalocyanine dyes to determine the color of light emitted by stars. This allows astronomers to study the chemical composition and structure of stars, as well as their evolution over time.