1. Rising & Dipping of Lights

2. Terminology Luminous Intensity Meteorological Visibility Nominal Range Determining Luminous Range Geographical Range Expected Visible Range Use of Tables in Admiralty List of Lights Rising & Dipping Ranges. Scope

3. Luminous Intensity of a light Brightness expressed in candlepower, measured in Candelas Appropriate for scientific purposes only. Terminology

4. Luminous Range depends on: Nominal Range (given for a 10M visibility) Prevailing Meteorological Visibility Refer to Adm List of Lts: Luminous Range Diagram. Luminous Range Maximum distance a light can be seen, as determined by the intensity and the prevailing visibility. It takes no account of elevation, observer’s height of eye or the curvature of the earth.

5. Meteorological Visibility A measure of the transparency of atmosphere Distance over which a specified MARKER is visible - Greatest dist at which a black object of suitable dimensions can be seen and recognised against the horizon sky, or, at night, could be seen and recognised if the general illumination is raised to the normal daylight level - Expressed in ‘miles At sea – estimate distance. Terminology

6. Nominal Range of a light Visible range under a 10 mile Meteorological Visibility Appears on charts Appears in the Admiralty List of Lights Terminology Based on 10 mile Visibility

7. Determining Luminous Range Meteorological Visibility = 15 nm Nominal Range = 9 nm Luminous Range = ?? nm 11

8. Exercise: Refer to A.L.L Luminous Range Diagram. Nominal Range = 12 nm Meteorological Visibility = 20 nm Determining Luminous Range Luminous Range = ??? 18.5 nm

9. Caution: 1.Ranges are only approximate 2.Visibility (transparency of atmosphere) is not necessarily consistent between observer and the light 3.Glare from background lighting will reduce the range considerably. 20 mile nominal range of a light, with minor background lighting could reduce to about 14M and with major background lighting to about 9M. 4.Lights showing a very short flash may not be visible at the range calculated. 5.Frost/Ice on light can greatly reduce the sighting range Using the Luminous Range Diagram:

10. To obtain approximate visibility. If a light with a NR of 20M is sighted at 12 miles; then the meteorological visibility will be about 5 miles. Using the Luminous Range Diagram:

11. Maximum distance the light from a LIGHT can theoretically reach an observer, as limited only by: Curvature of earth Refraction of the atmosphere Elevation of light Height of eye of observer Geographical Range:

12. Determining Geographical Range Geographical Range depends on: Height of Eye Elevation of the Light Refer to A.L.L. Geographical Range Diagram.

13. Determining Geographical Range Metres or Feet ?

14. Exercise: Refer to A.L.L Geographical Range Diagram. Height of Eye = 6 m Elevation of Light = 14 m Determining Geographical Range Geographical Range= 12.6 nm

15. Expected Visible Range is the lesser of : Luminous Range Geographical Range Determining Expected Visible Range 18.5 nm 12.6 nm Nominal Range = 12 nm Meteorological Visibility = 20 nm Height of Eye = 6 m Elevation of Light = 14 m

16. Ship is within the Luminous Range but beyond the Geographical Range. The loom of the light is visible but not the light. Ship is within the Luminous Range and the Geographical Range. Light is visible. Ship is within the Geographical Range but beyond the Luminous Range. Light is not visible, but the structure is visible by day.

17. Determine range – by observing Rise/Dip of light Possible when Luminous Range > Geographical Range Rising & Dipping Ranges 18.5 nm12.6 nm

18. Terminology Luminous Intensity Meteorological Visibility Nominal Range Determining Luminous Range Geographical Range Expected Visible Range Use of Tables in Admiralty List of Lights Rising & Dipping Ranges. We covered: Rising & Dipping of Lights