Lights used as aids to navigation may emanate from lighthouses, light vessels, buoys or beacons. Lights on lighthouses and shore beacons may show a different colour light in adjacent sectors in order to indicate danger areas or a safe channel. Some important lighthouses may also show different light characteristics in adjacent sectors.  Where arcs of visibility are given on the chart, the bearings are true from seaward, measured clockwise from 000^o to 360^o.

   On the chart a full description of all lights is given in abbreviated form in the following order:-

 a.  Name or number of light (if any).

 b.  Characteristics or appearance of the light.

 c.  Colour or colours of the light.

d. Time taken to complete one complete cycle of the light pattern of illumination.

e. The height of the light source above mean sea level in metres / feet (in the Baltic).

f. On lighthouses and shore beacons, the visible range of the light in clear weather.

g. Any other details such as fog signal, signal station, radio beacon, etc.

   The principle characteristics are:-

Class of Light

Description

Abbreviation

a.

Fixed

A continuous steady light

F

b.

Flashing

Lit period shorter than the eclipsed period

Fl

c.

Group Flashing

Two or more flashes followed by longer eclipsed period

eg Fl(3)

d.

Quick Flashing

Continuous flashing at to 60 times a minute

Q

e.

Very Quick Flashing

100 or 120 flashes a minute

VQ

f.

Ultra Quick Flashing

More than 160 flashes a minute

UQ

g.

Interrupted Quick Flashing

Quick flashing periods followed by eclipsed periods

IQ

h.

Group Quick Flashing

Two or more eclipsed periods followed by longer lit periods

eg Q(2)

i.

Occulting

Long lit period followed by short eclipsed period

Occ

j.

Group Occulting

Two or more eclipsed periods followed by longer lit period

eg Occ(3)

k.

Isophase

Lit and eclipsed periods of equal duration

Iso

l.

Alternating

Alternate colours shown at equal and regular intervals

eg Al WR

m.

Fixed and Flashing

Fixed lights showing regular flashes of greater brilliance

F Fl

n.

Morse Code

Continuous flashing of one or more letters in the Morse Code

eg Mo(K)

   The colours of lights are abbreviated and shown as follows:-

   White  W (may be omitted)

   Red  R

   Green  G

   Yellow Y

   Blue Bu

   Violet Vi

   The time period of a light, is the time taken to complete one whole cycle of the characteristics of the light, that is from the start of one cycle to the start of the next.  This is shown on the chart in seconds, abbreviated to 's'.

   The theoretical range of visibility of a light, is given in sea miles, either as a single figure, or two figures where different colours of varying visibility are used.  They are shown thus:-

   Single Range  eg 20M

   Two Ranges    eg 16/12M

   Three or more Ranges  eg 20-16M

   Other details such as fog horn or radio beacon will be added in abbreviated form at the end of all other information concerning the light.  From this information a full description of any lighthouse is shown as:-

   Fl(3) WRG 20s 15m 18-12M

   This would indicate that it is a group flashing three light with white, red and green sectors, the light period is twenty seconds, the elevation is 15 metres, and the range of the three different colours is from eighteen to twelve sea miles.

Admiralty List of Lights

   Names, descriptions, locations in Latitude and Longitude and characteristics of individual lights can be found in the Admiralty List of Lights.  The list is particularly useful for confirming the identification of a light structure in daylight. It also contains tables of distances of visibility.