PEL sector light

Typical PEL sector lights will have a complete color change over 1 meter (sideways movement) when the mariner is 5 km from the beacon.

The main advantage to a PEL sector light is that it has very sharp transitions between colors (typical 0.05°) and is bright enough to be used in daylight with up to 10 Nautical Miles or 18.5 km visibility.

[6] The solution was a weather proof projector sector light which used colored filters instead of slides to illuminate safe passage during the day.

If the mariner saw red light, they would need to change course immediately to avoid collision with the Tokaapapa Reef which is semi submerged at high tide.

Consequentially of having their origins in the Physics and Engineering Department, projector style beacons are now called PELs although they are often marketed as Port Entry Lights.