noun
photographic magnitude
Technical term in astronomy; refers to the brightness of a celestial object as measured on a photographic plate, which may differ from visual magnitude.
写真等級は、天体の明るさを写真乾板で測定した値です。
Photographic magnitude is a value that measures the brightness of a celestial object on a photographic plate.
Compound of 写真 (photograph) and 等級 (magnitude, grade), referring to the magnitude of a celestial object as recorded on a photographic plate.