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One Tower, Two Lights

Forum to discuss all areas of lighthouse technology such as optics, fuels, fog signals, radiobeacons, daymarks, construction, etc.

Postby island » Thu Apr 24, 2008 5:25 am


This is a lighthouse technology trivia.

On the East Coast there is a traditional lighthouse with a single tower of earlier period stone construction. This is apparently the only light station on this coast and possibly the only one in the U.S. lighthouse system that has two active aid-to-navigation lights; one light located directly above the other.

What light station is this and why does it have two lights?
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Postby Hersh » Thu Apr 24, 2008 10:20 am


New Cape Henry has the original Fresnel lens in the lantern and a smaller aerobeacon looking thing under it outside.

But I'm guessing that this isn't what you're thinking of because Henry is a masonry tower, I think...

I'm not precisely sure why Henry has this arrangement though.
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Postby island » Thu Apr 24, 2008 8:09 pm


The light station with the two lights is north of Cape Henry. It is closer in age to that of Old Cape Henry than New Cape Henry.

I have no idea what that aerobeacon like light is for. It is mentioned in the Cape Henry entry in the District 5 Light List
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Postby Grover1 » Thu Apr 24, 2008 8:19 pm


Part two would appear more apparent than part one ...

It must have two beacons to mark two separate passages ...

(and a pleasure, Dave, to see you amongst us ... it has been awhile)
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Postby island » Thu Apr 24, 2008 9:00 pm


One light is for a more general purpose while the second is in fact to mark a specific passage.
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Postby Hersh » Fri Apr 25, 2008 6:08 am


Now that I look again, the aerobeacons may jut be aircraft warning lights for daytime use.

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Since I know little to nothing of east coast lights, I'm out of this discussion...
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Postby ron » Fri Apr 25, 2008 1:34 pm


looks to me to be an emergency light in case the main goes down. we have lots of these because of the time it takes to service the main We could be months getting back to the station
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Postby island » Fri Apr 25, 2008 5:59 pm


More hints--

The lighthouse in question is of Colonial period and is in New England. It is one that is relatively popular for tourists. It is the subject of a recent book, but the second light is not mentioned in the text.

As Ron stated this appears to be the auxiliary light that automatically illumiates if the main light fails. At many lights this light is mounted on a trolly on a metal pole and the light is elevated above the top of the light tower.
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Postby wheland » Fri Apr 25, 2008 9:12 pm


I'm going to guess Portland Head based solely on the last post.

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Postby AL » Sat Apr 26, 2008 4:40 pm


Highland Light on Cape Cod has two lights.
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Postby island » Sat Apr 26, 2008 7:26 pm


The answer I was looking for is Portland Head. The traditional light at the top of the tower identifies the general location of the harbor entrance. This second light is a Directional Light that aligns with the main approach from offshore for large ships to safely enter the outer harbor. This light is located near ground level beside the fog signals in front of the fog-signal building and has a focal plane 23 feet above sea level. This light displays a narrow beam of three colors; white in the center, red and green on either side. It is illuminated day and night and is high intensity for day visibility with a range of 15 miles for the white and 11 miles for the red and green.

A Directional Light is a modern range light. The older range lights are a combination front light and rear light, aligned to identify the center line of the channel for which they serve. With a Directional Light only one light is needed. These lights have been and are being installed to replace the older range light combinations.

The optics are similar to that used in motion picture projectors to produce a beam with sharp cut-off boundaries between colors. When approaching this light from the right side of the channel one would see the red light only. Moving to the left, both red and white would be seen. Only white would be seen when in the center of the channel. Further to the left the light shows white and green, and green only to the far left. This light has proved to be a valuable aid for piloting large ships in and out of Portland Harbor.

Vega, Co of New Zealand manufactures these and other new design navigation lights.
http://www.vega.co.nz/default.aspx?Page=28
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Postby ron » Sun Apr 27, 2008 7:38 pm


we call them sector lights and they come in variations of 2 degree increments of the clear section depending on the channel width
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Postby Grover1 » Sun Apr 27, 2008 7:48 pm


Would I have heard about these regarding the Kennebec River lights?
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Postby island » Sun Apr 27, 2008 9:02 pm


Ron:
The Portland Head Directional bearings and degrees are:
Overall subtense 8 degrees
red 271.3 to 274.3 (3.0 degrees)
white 274.3 to 275.8 (1.5 degrees)
green 275.8 to 279.3 (3.5 degrees)

On the St. Lawrence Seaway at Bayfield Island there is an oscillating Vega directional light with the following charactistics from right to left:
Flashing R 268.250 to 268.675
Fixed R 268.675 to 269.325
Alternating WR 269.325 to 269.925
(W phase increasing with bearing}
Fixed W 269.925 to 270.075
(G phase increasing with bearing)
Alternating WG 270.075 to 270.675
Fixed G 270.675 to 271.325
Flashing G 271.325 to 271.150

Grover:
The range lights on the Kennebec are the Doubling Point Range Lights. These are the traditional two light front and rear combination. The front is 18 feet high and the rear is 33 feet high, 235 yards from the front. The lights are only visible 4 degrees each side of the range center line.
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Postby Grover1 » Mon Apr 28, 2008 2:30 am


I was thinking more along the lines of Squirlrel Point or Perkins Island ... The Lighthousefriends site cites an 1892 report, The Annual Report of the Lighthouse Board for 1892, “at Squirrel Point a fixed red light from a lens lantern, with a white sector to the southward, at an estimated cost of $4,650.”

I had remembered hearing this before and when you mentioned "sector" it rang a bell ... would this be the same idea you were describing at Portland Head?
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