Editing Leading lights (section)

==Operation==
Two lights are positioned near one another. One, called the front light, is lower than the one behind, which is called the rear light. At night when viewed from a ship, the two lights only become aligned vertically when a vessel is positioned on the correct bearing.<ref>{{cite book |last1=Bowditch |first1=Nathaniel |title=The American practical navigator : an epitome of navigation |date=2002 |publisher=Paradise Cay Publications |location=Bethesda, Md. |isbn=9780939837540 |page=64 |edition=2004}}</ref>

During the day, the lights may not easily be seen and therefore leading lights are often fitted with secondary visual aids, e.g. large red flags with wide black lines running down them. When both red flags and black lines line up, the navigator knows that the vessel is on the correct bearing. The structures are usually painted to make them more prominent.

Some major rivers, such as the [[Elbe|Elbe River]] in [[Germany]], have a series of leading lines. When it is necessary to make a turn, the navigator lines up the next pair of leading lights. This provides guidance from [[Hamburg]] to the sea, using successive pairs of leading lights.<ref>{{cite book |last1=Wendemuth |first1=Ludwig |title=The port of Hamburg, with plans, charts and numerous illustrations |date=1927 |publisher=Meissner & Christiansen |location=Hamburg |oclc=586327105 |page=204}}</ref>

Leading lights were used in Great Britain as early as 1763 to mark the [[Port of Liverpool]].<ref>{{cite book|title=Lighthouses of Liverpool Bay |first=John |last=Robinson |first2=Diane |last2=Robinson |publisher=[[The History Press]] |year=2007 |isbn=978-0752442099}}</ref> The first set of range lights in the [[United States]] were privately established by subscription at [[Newburyport, Massachusetts|Newburyport Harbor]] in [[Massachusetts]] in 1788.<ref>{{cite book |last1=Roberts |first1=Bruce |last2=Shelton-Roberts |first2=Cheryl |last3=Jones |first3=Ray |title=American lighthouses : a comprehensive guide to exploring our national coastal treasures |date=2012 |publisher=Globe Pequot Press |location=Guilford, Conn. |isbn=9780762779604 |edition=3rd}}</ref>

Leading lights are sometimes designed to be movable, allowing their position to be shifted in the event of a change in the safe channel; these include one at [[Hilton Head Range Rear Light|Hilton Head, South Carolina]], the original [[Chatham Light]], and the [[Nantucket Beacon]], predecessor to the Nantucket Harbor Range shown above.