Translation of Light
Translation of light is where a planet separates from one significator - by conjunction or aspect - and immediately applies to another (whilst still within orb of the planet it is separating from). It carries the influence of the former to the latter and thereby creates a connection between them. Some references suggest a need for the transferring planet to be received by the planet it is separating from or applying to.
Lilly writes of translation (CA., p.111)
Translation of light and nature is, when a light Planet separates from a more weighty one, and presently joins to another more heavy; and its in this manner, Let Saturn be in 20. degree. of Aries: Mars in 15 of Aries, and Mercury in 16 of Aries; here Mercury being a swift Planet separates from Mars, and translates the virtue of Mars unto Saturn. Its done also as well by any Aspect as by Conjunction. And the meaning hereof in judgment, is no more then thus; That if the matter or thing were promised by Saturn, then such a man as is signified by Mercury shall procure all the assistance a Mars man can do unto Saturn, whereby the business may be the better effected; in Marriages, Lawsuits, and indeed in all vulgar questions Translation, is of great use, and ought well to be considered.
Nicholas De Vore writes in his Encyclopedia of Astrology:
The conveyance of influence which occurs when a transiting planet, while separating from an aspect to one planet is found to be applying to an aspect to another, in which event some of the influence of the first aspected planet is imparted to the second aspected planet by a translation of light. For example, assume an Horary Figure in which Jupiter or Saturn, the Significators of the parties to the negotiation of an agreement, are in no aspect to each other; but Venus while separating from Jupiter is applying to an aspect of Saturn. There results a translation of light from Jupiter to Saturn, which is a powerful testimony that Venus represents a person or an idea that will bring about a settlement. The nature of the aspect, and of the aspecting and aspected planets through which the translation is accomplished, determines whether the outcome will be fortuitous.