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7th & 8th Order Fresnel Lenses

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Postby Zachary » Fri Mar 25, 2005 4:54 pm


On this page (Click) it says that there are 7th & 8th order fresnel lenses. Does anyone have a picture of one (or both) of these orders and information on the size of an 8th order?
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Postby Hersh » Fri Mar 25, 2005 5:23 pm


I don't think I've ever seen one that small....

I'd be curious to see what you find on this one.
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Postby island » Fri Mar 25, 2005 7:13 pm


The table of sizes on the above website shows two sizes for the 3-1/2 Order lens. There should be a space in the size columns following the entry for 3-1/2 Order. There are eleven orders total. The 8th order is the 75mm lens.


Hyper-Radial----1330mm
Meso-Radial- ---1125
First-Order -------920
Second-Order ---700
Third-Order ------500
Three and One-Half-
Order*------------
375
Fourth-Order-----250
Fifth-Order-------187.7
Sixth-Order------150
Seventh-Order--100
Eighth-Order------75
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Postby Hersh » Fri Mar 25, 2005 11:02 pm


I've never heard of the radial types, anyone have a shot of those?
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Postby Terry_Pepper » Sat Mar 26, 2005 2:05 am


Hyper-radiant and the even larger meso-radiant lenses were indeed manufactured at the turn of the twentieth century by the French, however no mesos were ever installed by the US lighthouse Service, and the only hyper-radiant installed in the US was at Makapuu Point on the Hawaiian island of Oahu.

According to page 33 of a USHLS report titled United States Lighthouse Service, 1915:

The largest lens in use in the Lighthouse Service at present is that at Makapuu Point, Oahu, Hawaii, the landfall light for vessels bound from the States to the Hawaiian Islands. This is of the hyper-radiant order, a larger size than those regularly listed, and has a focal distance of 1,330 millimeters, or 52.4 inches; the inside diameter of the lens is therefore nearly 9 feet, and it is enclosed in a specially designed lantern of 16 feet inside diameter. It is the only one of its type in the Service.

Here’s a photo of the lens from the US Coast Guard Historian’s Office website:

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Out of interest, this same report lists there were 766 Fresnel-style lenses in the Service as of June 30, 1915, distributed as follows:

First Order 57
Second Order 29
Third Order 68
Third-and-a-half Order 21
Forth Order 350
Fifth Order 155
Sixth Order 86
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Postby island » Sun Mar 27, 2005 6:55 pm


More on hyper-radials---

The first hyper radial lens was designed by David and Charles Stevenson, in consultation with Leonor Fresnel, and first constructed in 1885. These large lens required oil or gas burners of large focal diameter, i.e. many wicks or many gas jets.

The need for these large lenses diminished with subsequent improvements of illumination apparatus, the application of incandescent petroleum burners, for example. It then became possible to produce a beam of light from a 2nd Order lens of equal intensity to the hyper radial.
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Postby vacastle » Sun Mar 27, 2005 8:54 pm


So what about the 7th & 8th orders...where were they used?
Photos?

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Postby Hersh » Sun Mar 27, 2005 9:45 pm


Thanks for the info on the big boys, I definitely learned something new !!!

Now for the small fry...
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Postby Terry_Pepper » Sun Mar 27, 2005 10:36 pm


I have never come across any official reference to any of the seventh and eighth order lenses being used here in the US.

I seem to remember reading somewhere that they were used in Scotland and France for marking minor obstructions on rivers and in harbors, and also as marker lights on steam boats, but would love to see some definitive reference information on them if anyone can come up with any.
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Postby island » Mon Mar 28, 2005 12:06 pm


The only thing I have found about use of the small lenses that is credible is on Tom Tag's page at the beginning of this topic. "The Eight-Order lenses were used almost exclusively in Scotland. In America, the Seventh-Order lenses were called Steamer Lens Lanterns.."

I also note that there were no 7th or 8th Order lenses listed on the ALCC lens inventory. http://www.alcc.info/Lenses/complete_listing.htm
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Postby Forchu » Mon Mar 28, 2005 12:24 pm


been meaning to go to Hawaii to see that lens.
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Postby island » Mon Mar 28, 2005 2:11 pm


The lens at Sambro (NS) and Cape Race (NF). were the hypers or were they 1st Order? I have seen them listed either way. A photo I have seen of the Cape Race lens looks to me like a four sided hyper.
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Postby Terry_Pepper » Mon Mar 28, 2005 2:46 pm


I have copies of the Great Lakes sections of all Lighthouse Board and Lighthouse Service annual reports from 1852 through 1929 in my collection, along with copies and originals of 49 Light Lists from 1841 through 2004, and I have never come across any references to either Seventh or Eighth Order Fresnel-style lenses in any of them.
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Postby island » Mon Mar 28, 2005 4:16 pm


And what is a Steamer Lens Lantern? Such is mentioned on some websites but not described or illustrated.
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Postby Zachary » Mon Mar 28, 2005 4:28 pm


Could this be a 7th or 8th order Fresnel?
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