Text in force at 27-51: from 27-0, effective 1 Feb 1965.
The instrument lights must--
(a) Make each instrument, switch, and other devices for which they are provided easily readable; and
(b) Be installed so that--
(1) Their direct rays are shielded from the pilot's eyes; and
(2) No objectionable reflections are visible to the pilot.
29 FR 15695 · Source