Celestial photometry

Japanese: 天体測光 - てんたいそっこう（英語表記）celestial photometry

The accurate measurement of the amount of light from a celestial body. In practice, color filters for different wavelengths ( U ultraviolet, B blue, V yellow) or narrower interference filters are used to determine the amount of light in each wavelength range as a magnitude, and the total is then assigned a physical meaning. Modern astronomical photometry includes photographic photometry, in which a star field photograph is taken with a telescope, and the darkness and diameter of the star image on the photographic plate are combined and measured with a photometer to determine the magnitude, and photoelectric photometry, in which a photomultiplier tube is attached to a telescope, the light received from the star is converted into an electric current, amplified, and recorded on an ammeter to measure the magnitude.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

天体からの光の量を正確に測定すること。実際には，波長別の色フィルター(U紫外，B青，V黄)や，より透過幅の狭い干渉フィルターを使い，それぞれの波長域での光量を等級として求め，それら全体の物理的意味づけを行う。近代的天体測光には，望遠鏡で星野写真をとり，写真乾板上の星像の黒みと直径をあわせたものを光度計で測定して等級を決める写真測光と，望遠鏡に光電子増倍管をつけ，受けた星の光を電流に変え増幅して電流計に記録させて等級を測る光電測光とがある。

出典　株式会社平凡社世界大百科事典第２版について　情報

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