by puddlepirate » Tue Jan 01, 2008 12:29 pm
Hi All
For goodness sake!!
Any lighthouse - including the one at Orfordness is an important navigational mark. They are designed to be seen by ships at sea and are usually screened from the landward side, as is the Orfordlight. The lamp emits a powerful light and the Orford light has a range of 30M (to seaward). The Orford light is sectored - red/white/green. Only one light is visible in each sector (or what would be the point of the sectors!) and the sectors indicate to a ship that it is approaching from a danger area (red) or from an area of safe water (green) or is viewing the light from some distance off or approaching it from seaward, i.e. not from along the coast (white). The light emits one flash every five seconds in each sector. Some lights have rotating sheilds to acheive this (NOT the same sheild as that which protects the shore from the light). It does not vary. The reason it does not vary is because the flash identifies the light. Some lights have groups of flashes, e.g. a group of three flashes every ten seconds. Orford flashes once every five seconds and any ship in any of the red/white/green sectors can time the flash and by reference to a chart will know that what they are seeing is the Orford light. This is hugely important to ships at sea. If you approach the Orford light from west of south, between the coast and 210deg (bearing from the light, not your course) you will see red and must alter course to seaward (starboard in this case). If you approach from east of north, between 038 and 047deg you will see red. If you approach from east of north between the shore and 038 deg you will see green. Between 210 deg and 047 deg you will see white. If running down the coast towards the Orford light you will be steering at least 190 (T) or you will be aground. On this course you will see Orford flashing green every five seconds and will be able to identify the light and alter to port (seaward) as required, unless you intend to enter Orford Haven, which is tricky and requires local knowledge. The light does NOT emit a visible beam inland between the coast to either the north or south, the sheild to the coastal side of the lamp room prevents this. From the lamp this shielded area is an arc extending from approx 245 (south of west) via west and northwest to just east of north, to approx 005deg. Halt said the light was on a bearing of 110deg. What he saw COULD NOT HAVE BEEN THE LIGHT BECAUSE IT DOES NOT SHOW TO 110deg. 110deg towards the light equals 290deg FROM the light and that is in the sheilded sector. If you doubt any of this get an admiralty chart and a nautical almanac and check it for youself. If he saw a light at 110deg then there was something between him and the Orford light. Further still, there is one thing odd about Orford light. It has a white light only at 28m visible for 30M (to seaward!) but flashes red and green from a height of 14m. The red light has a range of 14M and the green has a range of 15M. This means that the red/green is for coastal shipping and local vessels only, whilst the higher, white only light is for ships making their way up or down the North Sea. Thus the red and green lights are only 14m above sea level - approx 46ft. The primary white light is at 28m -some 14m higher. As only the very top of the lighthouse is visible from Capel Green, then only the white light would be visible, not the red or green. But as from Capel St Andrew, the light bears approx 140deg (from the light Capel St Andrew is at 320deg) then this too is in the shielded sector. So whilst it might be possible to see the top of the lighthouse, anyone looking at it would see only the back of the lamproom - and that is sheilded so I doubt they would see any light at all or if they did, it would be a very tiny speck of white light. From the light, east gate is in line with Butley Abbey on a bearing of approx 280 deg (bears 100 deg when viewed from east gate) but given that east gate is just over 6 miles from the light and remembering the inverse square law that applies to light, you won't see that at east gate, plus of course the light is going to flash every five seconds every night of the year so even if you did by some fluke manage to see it through the trees etc, then it would have flashed every single night, in exactly sthe same position.....white flash, one and one thousand, two and one thousand, three and one thousand, four and one thousand, five and one thousand, white flash....as long as the lamp is lit. Over and over again. Every single night, for years on end. Anyone who had been at east gate, Woodbridge as a guard for any length of time would and IF they could see it, know exaclty what it was and would inform any new guys joining the watch. It was NOT the lighthouse!!
I'm going to drive up to Orford this afternoon (I should get to east gate at about 4pm) and take my camera. The forest might have changed but the light will be eactly the same and I shall see for myself what the SP on duty at east gate would have seen - and will photograph it!!
Halt and the others reported seeing multi-coloured or red lights, not a single, white light flashing every 5 seconds. If they saw a red light then they must have been much nearer the coast and much further to the south of the light than they are reporting and even then, if they saw it/them on bearing of 110deg it still would NOT have been the Orford light.
Source:
Admiralty Chart SC2695; Leisure edition 2002. Crown copyright.
Section 22 Visual Navigaton Aids and Port Information; Reeds Nautical Almanac; Thomas Reed Publications (1992)
Note: Reeds (1992) states that the primary white light is visible for 30M. The Admiralty Chart gives this as 20M (2002). Therefore and to give the best case scenario, I have used Reeds in the text above as the light ranges shown in Reeds are greater than that of the Admilaty chart (which will have been based on a survey by the Hyrdrographer of the Navy).
You can fool all of the people some of the time and some of the people all of the time but you cannot fool all of the people all of the time (Winston Churchill)...causa latet, vis est notissima