Distance between range lights

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Postby island » Wed Apr 06, 2005 5:24 am

There is a pair of range lights in the US where the rear range light is located almost 4 miles inland from the front range light. The focal plane of the rear light is 75 feet* above that of the front light. What range is this?

*Correction: 131 feet, not 75 feet.
Last edited by island on Wed Apr 06, 2005 1:26 pm, edited 1 time in total.
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Postby Hersh » Wed Apr 06, 2005 9:35 am

Wow, that's a good one....
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Postby Pharoslvr » Wed Apr 06, 2005 10:04 am

The range of the rear light is 14.27 nautical miles

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Postby island » Wed Apr 06, 2005 1:24 pm

Error in the description above. :?

The height difference between front and rear is 131 feet as determined from the CG 2005 Light List, not 75 feet as I had stated incorrectly.
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Postby ron » Wed Apr 06, 2005 7:30 pm

well now you tell me after spending the looking for 75 feet separation
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Postby island » Wed Apr 06, 2005 8:01 pm

Sorry about that. Did you lean something new in your search?

Frankly I goofed when I used range light tower height instead of focal plane height when I posted the wrong difference in height. It did not look right so I went to the Light List and discovered my error.
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Postby bert911 » Thu Apr 07, 2005 8:26 am

Liston Range Lights, Fort Penn, DE?

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Postby island » Thu Apr 07, 2005 10:40 am

You got it, Bert.

The distance between Liston Range front and rear lights is unusually long, 6760 yards (3.8 statute miles). The rear fixed white light has a 2nd order lens and with a geographic range of 19+ miles but can be seen much further from the bridge elevation of the large ships transiting the very long Liston Range, said to be the longest in the U.S.. The southerly entrance to this range is about 24 NM from the rear light. The long distance to the entrance to the range is the reason for the long distance between range lights. If the range lights were too close together it would be difficult to use them for proper alignment when entering the range. The front range light has a focal plane of 46 feet and the light characteristic is Iso 6 seconds.

What range lights did you find initially using the wrong height difference I posted at first?
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