Navigation Lighting; Terms and Definitions

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jimh
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Navigation Lighting; Terms and Definitions

Postby jimh » Mon Feb 27, 2023 7:24 am

Regarding navigation lighting on boats with miniature electric incandescent light bulbs, here is a review of terms. The purpose of using proper terminology is to avoid confusion. Misuse of terms or invention of new meanings for long established terms only causes misunderstand and delay in communication.

The Miniature Incandescent Electric Light Bulb

The principal electrical characteristics of the light bulb are:
  • the operating voltage in Volts DC, which is typically 12-Volts or sometimes a slightly higher voltage like 13.2-Volts, as would be present in a fully-charged lead-acid six-cell battery;
  • the current consumed, usually in milliAmperes;
  • the power consumption in Watts (based on operating voltage and current), usually less than 10- or 20-Watts.

In incandescent light bulbs, the emitted light is generally considered to be white light when the light bulb is operating at its specified voltage. When operating at lower voltages an incandescent light bulb will tend to produce light that begins to shift away from white toward orange or red hues.

The Light Bulb Shape
The term "bulb" or sometimes "globe" or "shape" refers to the shape of the glass envelope in which the incandescent filament of the light bulb is contained. There are many shapes for the bulb or globe. These shapes are designated by codes used in the industry and are well understood. A letter generally indicates the general shape and a numerical suffix indicates the size. A common size for a miniature electric light bulb might be T3. In marine lighting an unusual shape called a Festoon is often used. Here is a chart depicting a number of families and sizes:

https://www.bulbs.com/learning/shapesandsizes.aspx

The Light Bulb Base
The bulb is connected to a base so that it can be used in an electric circuit and be easily replaced. There are many base types, organized in families like screw, twist lock, bi pin, bayonet, and wedge. For a good review of base types, see this chart;

https://www.bulbs.com/learning/basechart.aspx

The Light Bulb Socket
The miniature electric light bulb is then placed in a light bulb socket that matches the characteristics of its base. The light bulb socket is part of a lamp.

The Lamp
A lamp, specifically a navigation lamp, consists of a light bulb, a light bulb socket, usually a lens that focuses the light, and in some instance a color filter to change the chromaticity or color of the light, and a housing which often also restricts the emitted light to a particular arc of the horizon and permits mounting of the lamp onto the boat, which in some case will be by mounting atop a integral pole. When the lamp is illuminated the lamp produces light. A lamp is named after the type of light it creates. For example, a lamp that creates the light characteristics of a Port Sidelight is called a Port Sidelight lamp or a Red Sidelight lamp. A single lamp that creates both a Starboard sidelight and a Port Sidelight is called a Combined Sidelights lamp or sometimes a Red-Green Combined Sidelights lamp.

Light
With regard to boat Navigation Lighting, the term "light" refers to the illumination created and seen by other boats. For each light to be shown, there are specific characteristics that must be adhered to:
  • color of the light or its chromaticity
  • intensity of the light or its visibility measured in miles
  • location of the light on the boat, both fore and aft and athwartship
  • the height of the light above the water or above the boat gunwales,
  • the arc of the horizon over which the light is shown, and
  • the characteristic of the light, that is, steady or flashing.

Each light to be shown has a name. International and U.S. Coast Guard regulations define the name and the characteristics for each light that will be shown. The recognized names are:
  • sidelights
  • masthead light
  • sternlight
  • white all-round light
  • anchor light

A combination of navigation lights with these proper characteristics form the navigation lighting. For each type of boat and for each general circumstance of the boat's operation, regulations specify the navigation lighting. For smaller recreational boats there are generally only two types of navigation lighting to be shown:
  • when underway
  • when at anchor

When Underway
A small boat when underway is required to show sidelights, a single masthead light, and a sternlight. On small recreational boats, the sidelights can be combined into a single lamp with bi-color lens and mounted at the bow. This is not a "bow light" but many boaters mistakenly call them that. The correct name is a combined sidelight shown from the bow. When a combined sidelight lamp at the bow is used then the single masthead light and the sternlight can be combined into a white all-round light carried at the stern and not required to be on keel centerline. This is not a "stern light" but many boaters mistakenly call them that.

When at Anchor
A small boat at anchor outside of a recognized anchorage area is required to show an anchor light. On most small boats this is accomplished by illuminating only the white all-round lamp from the underway lights. Typically this will be possible because the electrical circuit for the white all-round light is separated from the combined sidelights, allowing it to be illuminated independently when at anchor.

Regarding the intensity of the light emitted by navigation lights and thus its visibility, the length of the boat is usually a factor. Larger boats are specified to show higher intensity lights that will be visible for long distance, perhaps as long as five miles. Smaller boats are specified to show less intense lights with shorter distances of visibility, perhaps as short as only one mile

For complete details of the navigation lights that must be shown, consult the International Regulations for Preventing Collisions at Sea, commonly referred to as "the ColRegs." You can read them on-line at

https://www.navcen.uscg.gov/navigation- ... malgamated

For definitions of navigations lights see PART C - LIGHTS AND SHAPES

https://www.navcen.uscg.gov/navigation- ... ted#rule20

Author's note: I recreated this article because it seems to have been stuck in several topic forums as a pinned article.