(1) The operation of obstruction lighting installed on obstructions of an over-all height greater than 150 feet above ground, or water if so situated, should be controlled by a light sensitive control device adjusted so that the lights will be turned on at a north sky light intensity level of about 35 foot-candles and turned off at a north sky light intensity level of about 58 foot-candles, or should be continuous.

(2) Under normal conditions, where no special means of controlling obstruction lighting has been recommended, either a light sensitive control device or an astronomic dial clock and time switch may be used to control the obstruction lighting in lieu of manual control.