Text in force at 25-153: from 25-72, effective 20 Aug 1990.
(a) The instrument lights must--
[ (1) Provide sufficient illumination to make each instrument, switch and other device necessary for safe operation easily readable unless sufficient illumination is available from another source; and]
(2) Be installed so that--
(i) Their direct rays are shielded from the pilot's eyes; and
(ii) No objectionable reflections are visible to the pilot.
(b) Unless undimmed instrument lights are satisfactory under each expected flight condition, there must be a means to control the intensity of illumination.
55 FR 29785 · Source