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Old Aug 3, 2008, 7:34 PM   #1
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I played with the concept of this challenge a little early this morning when I happened onto a very unusual sight. I'm used to seeing 8-10 Mourning Doves lined up on a power line, but this was ridiculous. Lighting was extremely harsh, coming in from directly behind the birds. I was shooting with the Sigma 50-500 and 1.4X teleconverter wide open, so DOF was very shallow. Near as I can tell, three birds are in sharp focus.

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style="BACKGROUND-COLOR: #000000"Paul
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Old Aug 3, 2008, 8:22 PM   #2
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Very cool!!
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Old Aug 3, 2008, 9:26 PM   #3
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Cool shot, Paul. It's almost as though they are weighing down the line. I don't think I've ever seen quite so many birds on one line.

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Old Aug 3, 2008, 10:22 PM   #4
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Neat! It's a mourning dove garland!
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Old Aug 3, 2008, 10:31 PM   #5
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nhmom wrote:
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It's almost as though they are weighing down the line.
They ARE weighing down the line. Each of those doves weighs one to two pounds. That many on the line have the potential for damage. I have seen lines with hundreds of smaller birds which probably create an even larger load. The wires are designed to handle wind loads but I don't know if they plan for bird loading or a combination of birds and wind.

Great shot.

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Old Aug 4, 2008, 4:27 AM   #6
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Paul,

Wow, that's impressive. 1.4X times 500mm quite a feat to keep everything stable.

Talk about splitting hairs.

The electric line without the birds forms a catenary. Any chain or similar string automatically creates a catenary when suspended freely. Not to be confused with the parabola used in some suspension bridges -- note the suspension cables are NOT allowed to be freely suspended thus they do not necessarily form a catenary.

Just trivia.. Aloha
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Old Aug 4, 2008, 12:01 PM   #7
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Well, first of all, I always thought it was spelled caternary and that a caternary is the suspended wire use to supply power to electrified railroads. I looked it up in my 100% and guaranteed accurate (sometimes) Webster's American Dictionary--College Edition. I was wrong on the spelling. The jury is still out on the curve formed by a suspended wire or cable. I was always taught both in physics and mathematics that it is a true parabola. The dictionary gives some trig formula and says a catenary is not a parabola. However if you analyze the force of gravity on the cable, any point on the cable has a line of gravity applied that is parallel to all other points. If you pass those lines through the curve and reflect them off the inside if the curve, they should converge on one "focal point"

OK, now it is time for our professor from the UK (aka farmer) to speak up.

However, what any of this has to do with the strength of the wire eludes me.

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Old Aug 4, 2008, 12:51 PM   #8
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nhmom wrote:
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Cool shot, Paul. It's almost as though they are weighing down the line. I don't think I've ever seen quite so many birds on one line.
Yeah. It reminds me of a movie I saw once.
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Old Aug 4, 2008, 1:34 PM   #9
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calr wrote:
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Well, first of all, I always thought it was spelled caternary and that a caternary is the suspended wire use to supply power to electrified railroads. I looked it up in my 100% and guaranteed accurate (sometimes) Webster's American Dictionary--College Edition. I was wrong on the spelling. The jury is still out on the curve formed by a suspended wire or cable. I was always taught both in physics and mathematics that it is a true parabola. The dictionary gives some trig formula and says a catenary is not a parabola. However if you analyze the force of gravity on the cable, any point on the cable has a line of gravity applied that is parallel to all other points. If you pass those lines through the curve and reflect them off the inside if the curve, they should converge on one "focal point"
As long as we're on an etymological tear, the related Italian word is "catenaccia," or "unbroken chain." It can also refer to a particular form of 3-5-2 soccer alignment in which two midfielders have the flexibility to become defenders or forwards depending on the flow of play. It was invented by the Italian national coach after a plane crash killed more than half of the national team on the eve of the 1962 World Cup and is still the favored method of play for the Italian team (and my soccer team, as well).

And this has even less to do with why the wire isn't breaking, lol. :?

Paul
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Old Aug 4, 2008, 8:11 PM   #10
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Great photo.
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