#astronomical

• Alcyone — The Romanian form of the mythological name Alcyone, daughter of Aeolus and wife of Ceyx. Devastated by her husband's death in a shipwreck, she threw herself into the sea, prompting the gods to transform them both into kingfishers (halcyons). In astronomy, it refers to the brightest star in the Pleiades open cluster (Eta Tauri), located in the Taurus constellation.
• Almucantar — A terminological variant for almucantar, designating a small circle on the celestial sphere parallel to the horizon where all points share the same altitude; the term is also used to name a special astronomical instrument (a modified meridian transit circle) designed to measure time and stellar coordinates as they cross the same parallel of altitude.
• Anagalactic — Located, occurring, or extending beyond the limits of our galaxy (the Milky Way); situated in extragalactic space. In a cosmic structural sense, the term applies to celestial objects, radiations, or astronomical phenomena (such as nebulae, galaxy clusters, or cosmic rays) that originate or evolve outside the stellar system to which Earth belongs.
• Analemma — An outdated graphical or spelling variant (or directly modeled after Latin/English) for the standard term 'analemă' (analemma). It designates the geometric figure-eight curve representing the annual variations of the Sun's position in the sky at a fixed hour, caused by the Earth's elliptical orbital motion.
• Setting — The act of setting and its result; the moment a celestial body sinks below the horizon (sunset, sundown); in an old technical or legal sense, it represents the act of annexing, attaching, depositing, or adding a document or evidence to an existing file.
• To set — To sink below the horizon, to disappear from view (said of the sun, moon, or other celestial bodies), marking the end of the day or the visibility interval of that star; to set. In a figurative, delicate, and literary sense, the term means to pass away, to die, to fade, or to gradually lose one's brightness, glory, or structural importance over time.
• Astroclimate — The totality of local physical and meteorological characteristics of the Earth's atmosphere (turbulence, transparency, humidity, number of clear nights, thermal stability) that influence the quality, clarity, and precision of ground-based astronomical observations. Assessing an astroclimate is essential for determining the optimal location of major astrophysical observatories, aiming to minimize optical distortions caused by the air mass.
• Astronomy club — An association, organization, or cultural-scientific club formed by amateur astronomers, professionals, and cosmology enthusiasts, aiming to promote astronomy, organize public celestial observations, technical workshops, and expeditions for viewing eclipses or meteor showers. This community structure provides members with access to shared optical instruments, databases, and mentoring platforms for astrophotography or observational research.
• Astrophysical — Belonging to astrophysics, relating to astrophysics; referring to the application of the laws, methods, and principles of physics to the study of the structure, chemical composition, evolution, and dynamic phenomena of celestial bodies (stars, planets, galaxies, black holes) and interstellar space. It also defines the instruments, research, or mathematical models used to explain the behavior of matter and energy on a cosmic scale.
• Astrophotogrammetry — A specialized branch of practical astronomy and photogrammetry that deals with the precise determination of coordinate positions, shapes, dimensions, and distances of celestial bodies or planetary structures through measurements performed on astronomical photographs. This method is widely used in mapping planetary surfaces, establishing high-precision star charts, and calculating artificial satellite orbits by analyzing tracks left on photographic plates or digital sensors.
• 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.
• Astrophotometer — A high-precision astronomical instrument (equipped with photoelectric sensors or calibrated CCD/CMOS cells) used in astrophotometry to quantitatively measure the luminous flux, intensity, and brightness of radiation emitted by celestial bodies. This device allows comparing the magnitude of a target star with a standard artificial light source or reference stars, forming the basis for calculating light curves of variable stars and detecting extrasolar planets.
• Astrograph — An astronomical refractor or telescope with a wide field of view, specifically designed and optimized for astrophotography, sky mapping, and astrometry. This optical instrument lacks an eyepiece for direct visual observation, instead focusing light directly onto a photographic plate (historically) or a large-scale electronic digital sensor (CCD/CMOS), enabling the precise recording of star and galaxy positions.
• Astrography — A descriptive branch of practical astronomy or an archaic terminological variant for astrophotography, having as its object the description, mapping, and cataloging of celestial bodies through images obtained using an astrograph. In a historical sense, it represents the technique of printing and faithfully reproducing star charts or photographic plates based on silver emulsion, used intensively in major international sky inventory projects of the 19th and early 20th centuries.
• Astrometric — Belonging to astrometry, relating to astrometry; referring to the precise geometric measurement of positions, angular distances, and proper motions of celestial bodies on the celestial sphere. This term defines the methods, coordinate catalogs, instruments (such as scanning telescopes), or satellite data (such as those provided by the Gaia mission) used to establish fundamental star charts.
• Astronomically — In an astronomical manner, according to the laws, methods, or principles of astronomy; from an astronomer's point of view. The term is used restrictively or stylistically to describe an action performed with space science rigor, such as calculating the exact position of a celestial body or measuring sidereal time relative to the night sky.
• Astronomical — Belonging to astronomy, relating to astronomy; based on the laws, methods, and principles of studying celestial bodies. In colloquial, journalistic, or economic language, the term is used hyperbolically to describe a huge, exaggerated, substantial figure, sum of money, distance, or proportion that exceeds ordinary limits and recalls the vastness of cosmic dimensions.
• Astroscope — A simplified optical instrument or astronomical device used historically or for educational purposes for the direct observation, visual examination, and projection of star charts onto the night sky. In older technical terminology, it defined a device equipped with interchangeable discs that aided in the rapid identification of constellations and planetary positions, functioning as a mechanical precursor to modern portable planetariums.
• Astrospectroscopy — An elite branch of practical astrophysics dealing with the photography, digital recording, and structural analysis of the electromagnetic radiation spectra emitted or absorbed by celestial bodies. By decomposing stellar light using prisms or diffraction gratings attached to telescopes, astrospectroscopy enables the determination of chemical composition, temperature, pressure, radial velocity, and magnetic field strength of objects in the universe.
• Astrospectroscopy — A fundamental field of astrophysics dealing with the qualitative and quantitative study of the electromagnetic radiation spectra emitted or absorbed by celestial bodies. This discipline analyzes spectral lines decomposed via diffraction gratings or prisms to deduce the chemical composition, effective temperature, surface gravity, radial velocity, and rotational motions of cosmic objects in the universe.