An Etymological Dictionary of Astronomy and Astrophysics

Same as → night blindness; opposite of → hemeralopia.

Etymology (EN): L.L. nyctalopia, from Gk. nukt, → night + al(aos) “blind” + -opia, akin to ope “view, look,” ops “eye.”

Etymology (PE): Šabkuri, from šab, → night, + kuri “blindness,” from kur, → blind.

Same as → night blindness; opposite of → hemeralopia.

Etymology (EN): L.L. nyctalopia, from Gk. nukt, → night + al(aos) “blind” + -opia, akin to ope “view, look,” ops “eye.”

Etymology (PE): Šabkuri, from šab, → night, + kuri “blindness,” from kur, → blind.

The mean square noise voltage across a resistance in thermal equilibrium is four times the product of the resistance, Boltzmann’s constant, the absolute temperature, and the frequency range within which the voltage is measured. → Johnson-Nyquist noise.

See also: Named after Harry Nyquist (1889-1976), a Swedish-born American physicist, who made important contributions to information theory. → Johnson-Nyquist noise; → formula.

The mean square noise voltage across a resistance in thermal equilibrium is four times the product of the resistance, Boltzmann’s constant, the absolute temperature, and the frequency range within which the voltage is measured. → Johnson-Nyquist noise.

See also: Named after Harry Nyquist (1889-1976), a Swedish-born American physicist, who made important contributions to information theory. → Johnson-Nyquist noise; → formula.

The highest frequency that can be determined in a Fourier analysis of a discrete sampling of data.

See also: → Nyquist formula; → frequency.

The highest frequency that can be determined in a Fourier analysis of a discrete sampling of data.

See also: → Nyquist formula; → frequency.

The minimum number of resolution elements required to properly sample a signal, such as a star image, without causing erroneous effects known as aliasing. For electronic imaging, this number is generally taken as 2 pixels across the seeing disk diameter at the half intensity points. Also called → Shannon’s sampling theorem and → sampling theorem.

See also: Named after Harry Nyquist (1889-1976), a Swedish-born American physicist, who made important contributions to information theory, and Claude Elwood Shannon (1916-2001), an American mathematician and pioneer of information theory; → theorem.

The minimum number of resolution elements required to properly sample a signal, such as a star image, without causing erroneous effects known as aliasing. For electronic imaging, this number is generally taken as 2 pixels across the seeing disk diameter at the half intensity points. Also called → Shannon’s sampling theorem and → sampling theorem.

See also: Named after Harry Nyquist (1889-1976), a Swedish-born American physicist, who made important contributions to information theory, and Claude Elwood Shannon (1916-2001), an American mathematician and pioneer of information theory; → theorem.