#variable stars

• Argelander — The surname of the celebrated German astronomer Friedrich Wilhelm Argelander (1799–1875), globally renowned for his fundamental contributions to observational astrophysics and stellar cartography. He coordinated the creation of the 'Bonner Durchmusterung' catalog (1859-1862), a reference structural work recording the position and magnitude of over 324,000 northern hemisphere stars, revolutionizing the study of variable stars and setting modern standards for astronomical photometry.
• Astrophotometry — A fundamental branch of practical astrophysics that deals with measuring the intensity, flux, and brightness of radiant energy (light) emitted by celestial bodies across different bands of the electromagnetic spectrum. Data obtained through astrophotometry (using photometers or CCD sensors) allow astronomers to determine cosmic distances, surface temperatures, rotational periods of variable stars, and to detect exoplanets via the transit method.