A node indicates that nautical sunset twilight time is detected/calculated.

Nautical twilight is the period when the center of the Sun is between 6 and 12 degrees below the horizon, when bright stars are still visible in clear weather and the horizon is becoming visible. It is too dark to do outdoor activities without additional lighting.

In the morning, nautical twilight starts at nautical dawn, when the Sun rises above 12 degrees below the horizon; it ends when the Sun's center reaches 6 degrees below the horizon. In the evening, nautical twilight begins when the Sun sinks below 6 degrees; it ends at nautical dusk, when the Sun is lower than 12 degrees below the horizon.

For locations north of 54°34' N or south of 54°34' S latitude, the Sun will never be lower than 12 degrees below the horizon for a period in the summer.

Technically, the start and end times are when the true geocentric position of the Sun is 102 degrees from the zenith position.

 | Data byte | Description                                                        | 
 | :---------: | -----------                                                        | 
 | 0         | User specified.                                                    | 
 | 1         | Zone for which event applies to (0-255). 255 is all zones.         | 
 | 2         | Sub-zone for which event applies to (0-255). 255 is all sub-zones. | 
