Using a watch for navigation - why do we point 12 toward the sun?

Randall

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I've been mentally toying with the differences between navigating with an analogue watch in the southern and northern hemispheres. In the southern hemisphere we're told to point the 12 toward the sun, then bisect between the 12 and the hour hand to find North. In the northern hemisphere, they're told to point the hour hand at the sun, then bisect between the hour hand and the 12 to get South. It seems that we could do it either way; if we point the hour hand at the sun, then bisect between the hour hand and 12, the result seems to be the same. The only answer I come up with is bisect clockwise from the hour hand in the AM, bisect anti clockwise from the hour hand in the PM. I think that's it. That would hold true for how they do it in the Northern hemisphere too. Does any one know? I'm not too bright; I have written out the cardinal points on a piece of paper, and am using an analogue watch to try and figure this out :ROFLMAO: For example, most of us know that if we're facing somewhere East, North is going to be somewhere on our left. So we'd just know to bisect on that half of the watch in the morning. Point the 6 at the sun at 0600, then bisect on the left side of the watch between the hour hand (6) and the 12, you get 3. Point the 12 at the sun in the morning, then bisect to the left between the hour hand (6) and 12, you get 9. Either would seem to work. So the whole thing is if you know any one cardinal point, say North, and you know where the other cardinal points are in relation to North ie East is 90 degrees to your right, South is dead behind you etc, you can use either the hour hand or the 12!

OK, I think I've just found something else playing with my watch and cardinal points on paper; what I've just said doesn't work through Winter, when the sun is NE to NW (roughly speaking for me in Tassie). This also seems to explain the rule for the northern hemisphere too, where through winter the sun is SE to SW. Can anybody confirm or deny, or point out something I'm missing?
 
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barra650

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I tend to use this method a lot . Knowing the shift of the sun over the course of the year makes a difference .
 

Wentworth

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No answers here, but I've also wondered about the difference taught in the Northern hemisphere.
Will watch the thread with interest.
 

Randall

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I think I've sussed it out. It's to do with the mirror image; the northern hemisphere is our mirror image. If the US was opposite us on the other side of the equator (same time zone) we would be facing each other while taking a bearing from the sun. This is what happens now, although at different times, because they are on the other side of the equator but way over to our left.

I don't know why I couldn't figure it out. It helps if you draw a diagram with the cardinal points. Put a sun symbol due east and due west. Also put one NE and NW to emulate Winter. Then just try the two different ways - you'll see. If we use the hour hand, the 12 is always on the wrong side of the sun for the calculation to work. It is to the right of the sun, when it needs to be to the left of the sun. I really don't know how I missed this. If you're in the Northern hemisphere, the sun is generally to the South. So they need the 12 to the right of the sun for the calculation to work. If they point 12 at the sun, the hour hand would be on the left, so the calculation wouldn't work.

To emulate Northern hemisphere, just put a couple of sun symbols SE and SW to emulate their Winter. I assume mid summer is straight over head?

It is an awesome simple calculation. I really like it. No where near as handy as a compass. Although, I'm assuming by using a watch, we're getting true north, not magnetic north. That is one bonus. The main great thing though is that it forces us to understand, or take note, of how the sun moves throughout the year and the day. I shall use my watch whenever someone else is navving from now on. I'm going to use a diving watch - the rotating bezel can pull duty for compass points (N at 60, E at 15, S at 30, W at 45).

I haven't found much info on this technique. Lots of repetitive stuff about how to use it, but nothing in depth.

Another question; I'm assuming this is true North, or close to it given the limitations of time zones. Can anyone confirm if this is true?

And, where is our sun mid summer? Is it straight over head? Even here in Tassie? I assume it doesn't, and that's why it gets warmer as you travel further north.

Any other interesting info to add to this technique will be appreciated.
 
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Randall

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Unless you're on or north of the Tropic of Capricorn, the sun is never directly overhead if you're in Australia.
Even here in Perth, the sun will always be in the north. Tasmania, more noticeably so.
That is strange - loosely navigating I'm pretty sure I've had the sun due west in the evenings here. Obviously not mid Winter. OK, I still don't quite understand it. It looks like the Sun's arc for us is slanted. I think. For example, imagine half a metal hoop. Hold it vertically upright on the ground. One end is East, one end is West. Now, lay the top of the hoop down till it's at 45 degrees (I don't know what the angle really is, this is just for mental imagery). The top of the hoop is North. In the middle of the day, the sun is North, but we still get East sunrise, West sunset?

Ahh, yes, I think that's it. Just found this: it shows Summer solstice, Autumn equinox, Winter solstice, and Spring equinox. Awesome gif. It also kind of confirms what I've always thought; that Spring and Autumn have similar weather.

Probably what you already knew redtail, of course. And this also explains your statement. My limited imagination wasn't even close.

Anyone feel free to jump in and comment - this is all new to me. Any more information would be great.

I feel such a goose; all those years of navving with compass and map. Knowing this would have helped immensely - I've always used the sun to nav once I get a bearing with the compass (eg sun at right angles to my left shoulder, or a little forward or a little back etc).

26667
 
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Randall

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Unless you're on or north of the Tropic of Capricorn, the sun is never directly overhead if you're in Australia.
Even here in Perth, the sun will always be in the north. Tasmania, more noticeably so.
And bugger me! I had a read of your link. The sun is moving north 15 metres every year :mad:. It's cold enough here already :oops::mad::ROFLMAO:
 

Randall

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Great little GIF that, as you say.

Check your Sun set in the due West with a compass. You may be surprised.
That's how I know. I'm guessing it'll be soon if it isn't already. Summer for me is MTB generally. I still pull the compass out now and then, but usually just to confirm a track is running in the direction according to the map (if not, wrong track :ROFLMAO:). Or if there's a junction with an extra track or two not shown on the map - tends to happen a fair bit. There are usually more tracks than what is shown on the map. Mostly though I'm on tracks. Winter is when I get challenged navving off track and faint track (tracks that haven't been maintained for 20 years or so. There are quite a few of them here).
 
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