Angular distance (symbol δ) from the celestial equator. One of the coordinates, with right ascension, that defines the position of a heavenly body in the equator system. Declination is measured positi
vely (+) north or negatively (-) south of the celestial equator from 0° to 90°.
A mathematical operation that allows to restore the original input signal, such as an astronomical image or spectrum, to its state before being affected by the atmospheric turbulence and the transfer
function of the instrument.