He is able to recognize his wife in his lucid moments.
<those lucid bands that spread across the arctic sky and are known as the northern lights>
His lucid history of this grim subject is scrupulously accurate, so far as I am able to judge … —Richard A. Posner, New Republic, 8 Apr 2002
“You would like me to read to you?”“You would oblige me greatly by doing so, Dorothea,” said Mr. Casaubon, with a shade more meekness than usual in his polite manner. “I am wakeful: my mind is remarkably lucid.” —George Eliot, Middlemarch, 1872
The atmosphere, seen through a short space of half or three-quarters of a mile, was perfectly lucid, but at a greater distance all colours were blended into a most beautiful haze … —Charles Darwin, The Voyage of the Beagle, 1839
The stroke also set off a major crisis of presidential succession, as the debilitated and not entirely lucid president continued to cling to office and plan feebly for re-election. —Beverly Gage New York Times Book Review, 13 Dec 2009