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#### MrA

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Problem solved! Thanks to the crew of Sailnet.....getting ready for ASA 105 written test and for the life of me I can't figure these two problems out? any step by step solution would be greatly appreciated. Your are on a compass course of 300 degrees when you note the monument and the lookout tower on Cuttyhunk Island are in line. Using s Pelorus you determine that the transit formed by the monument and the tower is 130 degrees to starboard. What is the deviation of your compass for this heading?....and the second question is a compass course of 317 degrees and a pelorus transit of 064 degrees to starboard again solving for deviation. I'm too old to be school material, in my youth I was a math wiz but now too many brains cell have retired on me when I need them the most. I just don't understand the process to solve these questions thanks augie

#### MrA

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both problems were solve without a chart? answers were 005 and 003 west. That's why I'm perplexed. Since in both problems you are traveling in a north direction and the transit is behind you, solving the problems takes you through 360 degrees and here is where I get lost? anyway the teacher did it without a chart? was it that he knew the bearing? If I plot it on a Rose it still makes no sense to me or am I just going about the process to solving the wrong way thanks

#### MrA

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just Saturday morning I drove an hour to see the teacher, he's not teacher material too long in the Marines, he believes every new sailor should be as smart as he, well he solved the problems right in front of me and still I can't get back to his numbers T=299, V=015W, M =314, D=003W, C=317 and the other problem T=290, V 015W, M=305, D=005E, C=300, thanks

#### MrA

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I would draw a line through the lookout tower and Cuttyhunk Island
Then I would put a dot anywhere on the line preferably in open water.
Then through that dot pointing somewhere west of north I would draw a line through the dot so that the angle between my northwest line and my south east line was 130 degrees.
Then I would use a parallel rule to find out the magnetic heading of this second line.
The difference between the magnetic heading of the second line and 300 is your deviation.

There are real navigators on this forum but maybe this will get you started.

This is how I thought about it.

If you see the lookout tower and the Island in line then you have to be somewhere on a line that connects those two.
The only question is where on the line and which direction you are pointing.
We don't know nor care where on the line but we know we are pointing 130 degrees west of the line because that is what the Pelorus says.

Now we can tell what our magnetic heading should be.
If it doesn't match our compass the difference must be the deviation.

It looks like the second question is the same as the first just different numbers.

I'm just guessing here but does this make sense?
the chart is a permanent fixture on the kitchen table, in the AM I will calculate your reply thanks

#### MrA

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#### MrA

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^^^^ Refer to first post, the only known in problem 1 is your compass course of 317 degrees and a transit measured with a pelorus of 064 degrees to starboard and the 2nd question you have a compass course of 300 degrees and a pelorus transit of 130 to starboard. I am totally lost or I am missing something? I need help from the experts, I don't want to leave Galveston Bay for Florida and end up in Mexico. The above link is the instructors worksheet when I was there on saturday

#### MrA

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Mr A - what is the true bearing from the monument to the lookout tower.
like tempest I get 60T

#### MrA

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Solution

T bearing monument to lookout = 060

V = 15W (from my chart - is training chart different?)

M bearing monument to lookout = 075

D = 075 - 070 = 5 E

C = 300 (ships compass) +130 (relative bearing from pelorus) - 360 = 070

So how many of you have a pelorus on board?
thanks so much T was the key

#### MrA

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My chart shows only one tower

What is the true bearing between the towers?

Jack
I get 359T

#### MrA

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The solution

T = 359

V = 15 W

M = 014

D = 7 W

C = 317 + 064 - 360 = 021

Yes, I get the same, I'll double check my line and make sure T was 359, I see what I was missing in your solution thanks

#### MrA

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3 W is correct...the line is 003 deg.. not 359
I tried again last night, best I could come up with 000T, I will draw a thinner line a put on better glasses and see what I can come up with thanks

#### MrA

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I believe a one-degree bearing error at one nautical mile could put you just over a hundred feet off; but a five-degree error starts getting serious at a good 500 feet. With pencil and paper charts, a one-degree error seems quite easy to make.
on the tests 2 degree error is acceptable, first time I'm doing this and I agree with you the larger the error the farther off course you will be, I can see a lot of factors affecting the results like how thick your lines are, how good your glasses are, how good the light is, if the boat is rocking and of course how many beers you had, if you followed this post from the start, Jackdale asked me the bearing on a line I plotted, I measured it a 359-degrees, Tempest immediately came back with 003-degrees, which was right. I can only hope I will get better with practice, The best I could come up was 001-degree. and I was wondering do sailors even use charts anymore other than emergencies? and would flying and sailing require a similar skill set?

#### MrA

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I use paper charts to do my planning and plotting. I also know how to use electronic charts (I have three different ones on my Windows tablet). I also know how to use radar fix on paper charts.

I may be an exception. Believe I will be also

Being able to paper charts is a skill that should be learned before one starts to use the electronics
this is me now and I enjoy putting pencil to paper

#### MrA

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excellent thank you

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