EEL Posted March 19, 2008 Share Posted March 19, 2008 To follow up on an old thread regarding sectored lights and navigation, you can see a set of sectored lights on the channel from Popham to Bath. Notice how the width of the sectors is governed by navigational needs. Look at Squirrel Island down to Dix Island and you will see a set of linked sectored lights. What can I say, still lots of snow here so my kayaking fix is staring at charts and dreaming. Ed Lawson Quote Link to comment Share on other sites More sharing options...
gyork Posted March 19, 2008 Share Posted March 19, 2008 ...still lots of snow here so my kayaking fix is staring at charts and dreaming. Ed Lawson Ditto here (Concord, NH) Ed, where my Susie is perversely hoping for a few more storms (10") to break the historic record of ~10 feet. RE: light sectors-hoping to verify the chart projection from Fox Island Thoroughfare, whilst enjoying a full-moon paddle this summer at IAH. Gary Quote Link to comment Share on other sites More sharing options...
EEL Posted March 19, 2008 Author Share Posted March 19, 2008 RE: light sectors-hoping to verify the chart projection from Fox Island Thoroughfare, whilst enjoying a full-moon paddle this summer at IAH. Gary That could be very cool. I guess you would need to paddle up from Duck Harbor to Robinson Light to catch it and that would be a nice bit of coast for a night paddle too. Or paddle up to north end islands and the village in the afternoon, wander about the village, walk to Greenlaw's shop, eat dinner at the Inn at IAH, and paddle back in the moonlight. Now that would be great day. http://www.innatisleauhaut.com/ http://www.blackdinahchocolatiers.com/ Or are you thinking of going from IAH to Vinahaven at night? Now that would be a trip with the moon over your shoulder. Ed Lawson Quote Link to comment Share on other sites More sharing options...
Pintail Posted March 19, 2008 Share Posted March 19, 2008 Gary, Does IAH stand, perhaps, for International Airport, Hobart? If not, do please enlighten me... Quote Link to comment Share on other sites More sharing options...
gyork Posted March 19, 2008 Share Posted March 19, 2008 ... from Duck Harbor to Robinson Light to catch it Ed Lawson That's the tentative plan, but open to your other option, among others (?full-moon circumnav of IAH (Isle au Haut)) are you thinking of going from IAH to Vinahaven at night? Ed Lawson NOT in the plans, though I suspect such a passage, or similar ones, might be a reasonable voyage, given safe weather conditions, if one has spent the day island-bound due to high winds/weather challenges. Gary Quote Link to comment Share on other sites More sharing options...
EEL Posted March 19, 2008 Author Share Posted March 19, 2008 (?full-moon circumnav of IAH (Isle au Haut)) Not for this timid woodland creature. Ed Lawson Quote Link to comment Share on other sites More sharing options...
EEL Posted March 19, 2008 Author Share Posted March 19, 2008 Gary, Does IAH stand, perhaps, for International Airport, Hobart? One a pilot, always a pilot, eh? Ed Lawson Who fondly remembers those comforting words, "Don't worry, I wont's ask you to go anyplace dangerous." Just before the rescue started. Quote Link to comment Share on other sites More sharing options...
rick stoehrer Posted March 19, 2008 Share Posted March 19, 2008 Not for this timid woodland creature. Ed Lawson hee-hee-hee....well, that's on the agenda....don't know how we're gonna sell the womenfolk on it. wish me luck. Quote Link to comment Share on other sites More sharing options...
EEL Posted March 19, 2008 Author Share Posted March 19, 2008 hee-hee-hee....well, that's on the agenda....wish me luck. On the paddling or the convincing? Sounds like you will need to be a 5* husband before you can utilize those 5* paddler skills. Wonder who is authorized to give out those awards. I'm afraid I know one mean, strict assessor and their training has been demanding and unending. Ed Lawson Quote Link to comment Share on other sites More sharing options...
rick stoehrer Posted March 19, 2008 Share Posted March 19, 2008 On the paddling or the convincing? Sounds like you will need to be a 5* husband before you can utilize those 5* paddler skills. Wonder who is authorized to give out those awards. I'm afraid I know one mean, strict assessor and their training has been demanding and unending. Ed Lawson coming along or letting us go, i'd be happy with either although if they stayed ashore and kept the wine company, we could cover a lot more water....but whatever i can wheel, i'll take! i've learned to be happy with ANY victory! why do you think they all go to the bathroom at the same time? duh, they exchange husband behaviour modification techniques! and whatever the training has been, i wouldn't want her any other way! <okay, honey? can i go paddling this weekend?> Quote Link to comment Share on other sites More sharing options...
Pintail Posted March 20, 2008 Share Posted March 20, 2008 Would someone <please> enlighten me? What does IAH stand for? Damn these modern habits of acronyms, initials and abbreviations (as when having to listen to radio journalists use the expression "24/7" on air! Ghastly...) I do recognise MDI as meaning Mount Desert Island; but will someone elucidate? I honestly do not know what Gary is writing about -- and I think I have a right to know, after all... Yours, in earnest, etcetera! Quote Link to comment Share on other sites More sharing options...
spuglisi Posted March 20, 2008 Share Posted March 20, 2008 Would someone <please> enlighten me? What does IAH stand for? Damn these modern habits of acronyms, initials and abbreviations (as when having to listen to radio journalists use the expression "24/7" on air! Ghastly...) I do recognise MDI as meaning Mount Desert Island; but will someone elucidate? I honestly do not know what Gary is writing about -- and I think I have a right to know, after all... Yours, in earnest, etcetera! Isle au Haut it was buried back in the thread. Quote Link to comment Share on other sites More sharing options...
EEL Posted March 20, 2008 Author Share Posted March 20, 2008 Would someone <please> enlighten me? What does IAH stand for? .. I honestly do not know what Gary is writing about -- and I think I have a right to know, after all... Yours, in earnest, etcetera! I apologize. I thought you knew and were having your humorous way with it. If you get a chance, it is a very neat place to visit. The July 4th parade is a wonderment. Ed Lawson Quote Link to comment Share on other sites More sharing options...
gyork Posted March 20, 2008 Share Posted March 20, 2008 RE: light sectors-hoping to verify the chart projection from Fox Island Thoroughfare, whilst enjoying a full-moon paddle this summer at IAH. Gary Responding indirectly to a private E from Ed. Given clear skies and equidistant from Robinson Light and Trial Point (http://www.charts.noaa.gov/OnLineViewer/13302.shtml) will I, in fact, be able to see the sectored candle from the 41 ft tall tower, 9 NM away, whilst sitting in my kayak, eyes 3 feet above sea level? Who wants do to the math, while I go back to work? Pintail, I apologize for not answering your inquiry of Isle Au Haut more directly. Gary Quote Link to comment Share on other sites More sharing options...
EEL Posted March 20, 2008 Author Share Posted March 20, 2008 Given clear skies and equidistant from Robinson Light and Trial Point (http://www.charts.noaa.gov/OnLineViewer/13302.shtml) will I, in fact, be able to see the sectored candle from the 41 ft tall tower, 9 NM away, whilst sitting in my kayak, eyes 3 feet above sea level? Who wants do to the math, while I go back to work? Gary Rough guess would be that a light 41 feet up should be visible on clear night from a kayak at a distance of 8NM, but it would be right at the horizon. Basing this on the the formula that you take the square root of the height of the object and add 1.5 to get the distance at which an object will appear on the horizon to someone in a kayak under good conditions. Of course Gary has some advantage here. http://www.roguepaddler.com/distance.htm Ed Lawson Quote Link to comment Share on other sites More sharing options...
gyork Posted March 20, 2008 Share Posted March 20, 2008 the sectored candle from the 41 ft tall tower Oops! Chart shows light tower is 51 ft (NOT 41 ft). Quote Link to comment Share on other sites More sharing options...
gyork Posted March 20, 2008 Share Posted March 20, 2008 Rough guess would be that a light 41 feet up should be visible on clear night from a kayak at a distance of 8NM, but it would be right at the horizon. Basing this on the the formula that you take the square root of the height of the object and add 1.5 to get the distance at which an object will appear on the horizon to someone in a kayak under good conditions. Of course Gary has some advantage here. http://www.roguepaddler.com/distance.htm Ed Lawson From Ed's reference (thanks): Putting it all Together: To the Horizon and Beyond In case you missed it, we just combined our first two distance rules to calculate the total distance from the paddler to an object emerging over the horizon. Let's call this Distance Rule 3: Total distance =Sqr root (object height) + Sqr root (height at eye level) The total distance from the paddler to an object just emerging over the horizon (in miles) is equal to the square root of the object's height (in feet) plus the square root of the paddler's height at eye level (in feet). Because we know that the paddler's height at eye level is typically about two feet high and this value remains constant, we don't actually need to recalculate this part of the equation each time we apply the rule. So, the simplified version of Distance Rule 3 could read: The total distance from the paddler to an object just emerging over the horizon (in miles) is equal to the square root of the object's height (in feet) plus 1.5 miles. Sqr root (51) + Sqr root (2)=7.14 + 1.4 = 8.55 miles For me: Sqr root (51) + Sqr root (3)= 7.14 + 1.73 = 8.87 miles Assuming the formula is referring to statute miles (why?) then converted distances would be 7.4 NM for many and 7.7 NM for Carl, Jason, me, et al. Looks like I won't see it sitting in my kayak! How about standing in my kayak? D =7.14 + Sqr root (6) 2.45= 9.6 miles, 8.34 NM NOT QUITE, and I refuse to stand on my tippie-toes while standing in my kayak. I will head to shore and start climbing, expecting to see the light at (10.35 miles=7.14 + Sqr root (X)) TEN FEET. Quote Link to comment Share on other sites More sharing options...
EEL Posted March 20, 2008 Author Share Posted March 20, 2008 Looks like I won't see it sitting in my kayak! Actually, there is more to it than that. The following might seem to be more arcane than trivia, but it is nice stuff to know if you go upon the sea at night. The range (distance at which it can be seen) of a light as shown on a chart is its nominal range which is the maximum distance the light can be seen under essentially ideal visibility conditions without regard to the curvature of the earth. In other words, is a function of the intensity of the light. It says nothing about the range the light could be seen by a given person on a vessel on a given night. That is dependent upon the light's luminous range which is the range of the light under the given atmospheric conditions without regard to the curvature of the earth and its geographic range which is the maximum line of sight range for a given observer height which takes into account the curvature of the earth. In other words, to be visible, the observer must be at a range less than all three. The Coastal Pilot has tables for determining geographical range and the Lights List has charts for estimating luminous ranges. I have always assumed the square root calculation results were in NM which no doubt means they are in statute miles. Ed Lawson Quote Link to comment Share on other sites More sharing options...
gyork Posted March 20, 2008 Share Posted March 20, 2008 ...dependent upon the light's luminous range which is the range of the light under the given atmospheric conditions.... Ed Lawson Ed, the notation on the chart is 11M (11 nautical miles). Is this what you are referring to as "luminous range"? Am I correct in believing that the candlepower is of such strength that, under ideal conditions, I would see the illumination up to a distance of 11M, in a straight "line of sight"? It appears my planned leisurely expedition will now have stong scientific undertones! Full report to follow at a later date (June). Gary Quote Link to comment Share on other sites More sharing options...
EEL Posted March 20, 2008 Author Share Posted March 20, 2008 Ed, the notation on the chart is 11M (11 nautical miles). Is this what you are referring to as "luminous range"? Am I correct in believing that the candlepower is of such strength that, under ideal conditions, I would see the illumination up to a distance of 11M, in a straight "line of sight"? No, the range on the chart is the nominal range. Yes, the nominal range is the maximum distance under ideal conditions the light can be observed assuming it is in a straight line of sight. The Luminous range is the range at which the light could be seen under the atmospheric conditions existing at a given time. In other words, the luminous range would be far lower in haze than its nominal range and likely geographic range as well. Of course then there is the issue of how these ranges might be distorted/affected by other influences, but that is a subject for John Huth and the like who actually understand the physics behind this stuff. Ed Lawson Quote Link to comment Share on other sites More sharing options...
Pintail Posted March 20, 2008 Share Posted March 20, 2008 First: thank you, Gary and Ed: now I understand. Secondly: I also understand your concern about the visibility of a light forty or fifty feet up in the (comparative, as far as we lowly kayakers are concerned) stratosphere; but (surely?) this is academic. We are not discussing a <laser> here: a light beam has an increasing (with distance) beam width/depth, hasn't it? Consider a person standing on a beach, just a few miles from a light: that person still sees the beam despite being lower than its level of projection -- whatever the mathematicians say -- don't they? You can see a beam of light that passes <over> you, can't you? Why should this instance be any different? I am not trying to pooh-pooh what has gone before: I simply think that this question is limited by an over-academic approach? Maybe I am missing something you mean, here? The question about seeing the definition of the <quadrant> is much more interesting. Quote Link to comment Share on other sites More sharing options...
EEL Posted March 20, 2008 Author Share Posted March 20, 2008 Maybe I am missing something you mean, here? Nope. We to the North typically go stark raving mad through cabin fever about this time of year. Especially when we have an abundant snow year. Consequently we engage in odd behavior like staring at charts, reading the Coastal Pilot and engaging in obtuse conversations. Well, I rather doubt you can see a beam from the navigation lights in question without something to disburse the light and the beam being strong enough at your position. While I assume the light would actually be a cone from the source, the issue is when would the low edge of the cone be blocked by the curve of the earth and at what distance would you no longer see the light regardless due to becoming too dim due to haze, fog, whatever. On the other hand, if were reflected on a cloud or some such, then the distance could be quite long. However I think the purpose of sectored lights is to enable vessels to find channels or hazards and for that the width and intensity of the light is adjusted to suit the particular location. The light Gary is enamored with is quite narrow at 2 degrees for example as it marks a rather narrow way well inside the lane. While the Robinson light on IAH is not as narrow since it marks the outer edge of a way. Then there is the tri-colored light at Portland Head which marks the way to the way on the south side of Cushing. See what I mean about going stark raving mad? Actually, this thread has to stop. Given that perseveration is a marker for something or other. Ed Lawson Quote Link to comment Share on other sites More sharing options...
gyork Posted March 20, 2008 Share Posted March 20, 2008 Actually, this thread has to stop. Ed Lawson Yes, I'm out, at least for today. (I did get some work done today.) Gary (Snowbound, landlocked, kayaking gypsy) Quote Link to comment Share on other sites More sharing options...
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