Sailing at night on a sailboat can offer a wonderful view of the starry sky, a feeling of silence and peace but also a challenge of navigating at night. However, it is important to be prepared and take the necessary precautions to ensure a safe and enjoyable experience.


A lighthouse is a tower, building, or other type of physical structure designed to emit light from a system of lamps and lenses and to serve as a beacon for navigational aid, for maritime pilots at sea or on inland waterways.

Lighthouses mark dangerous coastlines, hazardous shoals, reefs, rocks, and safe entries to harbors; they also assist in aerial navigation.

Navigačné svetlá

Name: The name of the lighthouse

Fl(3): An abbreviation of the type of light

WGR: The color of the light, "W" for white, "G" for green, "R" for red

15s: The cycle period, "15s" for fifteen seconds

21m: The height of the light above the chart datum for height (usually based on high water). e.g. 21m for 21 metres.

15-11M: The range in which the light is visible (in nautical miles), e.g. "15M" for white light, „11M“ for green light, red light between white and green light.

Light patterns

Fixed light (F.)

Navigačné svetlá

A fixed light, abbreviated "F", is a continuous and steady light.

Flashing light (Fl.)

Navigačné svetlá

A flashing light is a rhythmic light in which the total duration of the light in each period is clearly shorter than the total duration of the darkness and in which the flashes of light are all of equal duration. It is most commonly used for a single-flashing light which exhibits only single flashes which are repeated at regular intervals, in which case it is abbreviated simply as "Fl". It can also be used with a group of flashes which are regularly repeated, in which case the abbreviation is "Fl(2)" or "Gr Fl(2)", for a group of two flashes.

Occulting light (Oc.)

Navigačné svetlá

An occulting light is a rhythmic light in which the duration of light in each period is longer than the total duration of darkness. In other words, it is the opposite to a flashing light where the total duration of darkness is longer than the duration of light. It has the appearance of flashing off, rather than flashing on. Like a flashing light, it can be used for a single occulting light that exhibits only a single period of darkness or the periods of darkness can be grouped and repeated at regular intervals (abbreviated "Oc"), a group (Oc(3)) or a composite group (Oc(2+1)). 
The term occulting is used because originally the effect was obtained by a mechanism (e.g. a vertical or rotating shutter) periodically shading the light from view.

Isophase light (Iso.)

Navigačné svetlá

An isophase light, abbreviated "Iso", is a light which has dark and light periods of equal length. The prefix derives from the Greek iso- meaning "same".

Alternating light (Al.)

NNavigačné svetlá

An alternating light, abbreviated "Al", is a light which shows alternating colors. For example, "Al WG" shows white and green lights alternately.


Q: Quick (50-79/min)
VQ: Very Quick (80-159/min)
UQ: Ultra Quick (more then 160/min)


Color of light:

R: Red
G: Green
W: White
Y: Yellow


Marinatips Team