An Etymological Dictionary of Astronomy and Astrophysics
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Photometry using a diaphragm to isolate a small sky area, either directly with a focal-plane diaphragm, or with an image processing system.

→ aperture; → photometry.

The measurement of the intensity of light of celestial bodies.

Astrophotometry, from → astro- + → photometry.

Axtar-šidsanji, from axtar-, → astro-, + -šidsanji, → photometry.

Photometric measurements carried out through filters with a band-width (about one-tenth the central wavelength) in the range 30-100 nm. Typical examples are Johnson photometry, Krons-Cousins RI photometry, and the six-color system.

→ broad; → band; → photometry.

Photometry using narrow-band filters to isolate a particular spectroscopic line or molecular band.

→ narrow band; → photometry.

A photometry in which the magnitudes are obtained using a photoelectric photometer.

→ photoelectric; → photometry.

In astronomy, the measurement of the light of astronomical objects, generally in the visible or infrared bands, in which a wavelength band is normally specified.

→ photo- + → -metry.

In astronomy, measurement of the absolute fluxes of the components of different frequencies in the spectrum of a light source.

→ spectrum; → photometry.

The precise measurement of a star's brightness, usually through several specific wavelength bands.

→ stellar; → photometry.

A photometric system with five wavelength ranges that does not use filters. Instead it uses prisms and lenses (spectroscopy) to select the bands simultaneously. The wavelengths and the bandwidths are: W, 3250 and 140 Å; U, 3630 and 240 Å; L, 3840 and 230 Å; B, 4320 and 450 Å; and V, 5470 and 720 Å. The Walraven photometer was unique in design and remained literally unique as copies were never built. In addition, during its whole life the photometer was mounted permanently on the same telescope that had been built specifically for this instrument, the 91 cm Lightcollector' reflector, which started in 1958 at the Leiden Southern Station in Broederstroom, South-Africa. After 20 years in South-Africa the telescope and photometer were moved to the European Southern Observatory La Silla observatory in Chile. The photometric observations were resumed in March 1979 and continued for another 12 years until the decommissioning of the photometer in 1991.

After the inventors, the Dutch astronomer Theodore Walraven (1916-) and his wife Johanna Helena Walraven, née Terlinden (1920-89); → photometry.