from The Century Dictionary and Cyclopedia
- n. The correction for the effect on astronomical phenomena, especially eclipses of Jupiter's satellites, of the time required by light to traverse the space between the planet and the earth. This is combined with aberration (which see).
Sorry, no etymologies found.
Glasenapp's "light-equation," with which it was combined, errs slightly by excess.
"mean radius" of the earth's orbit, is called the "light-equation"; and the determination of its precise value has claimed the minute care distinctive of modern astronomy.