Section 10(b) in The Merchant Shipping (Prevention of Collisions at Sea) Regulations, 1975
(b)In the case of sailing vessels the vertical sectors of electric lights shall ensure that:(i)at least the required minimum intensity is maintained at all angles from 5 degrees above to 5 degrees below the horizontal.(ii)at least 50 per cent of the required minimum intensity is maintained from 25 degrees above to 25 degrees below the horizontal.
