Celestial naviation

[Adi007]

Did I heard someone mention celestial navigation? ):

Well, here are three easy ways to spot Polaris (the North Star) using three of the easiest to spot constellations in the Northern hemisphere.

First, is using the ever popular Big Dipper (or Great Bear). Follow the two stars at the front to the next brightest star and you've found the North Star.

Next example uses Cassiopeia (the constellation that looks like a W). This one is easy to do!

Finally, finding the North Star using Orion the Hunter. This is a bit more tricky as it means you have to span a greater area of sky and Orion is really only in a good spot in Winter.

All you need is a clear night and a dark sky ... it's great fun. To make life easier you can print these images out (eventually I'll get around to making some that have black starts on a white background!).

Share your other celestial navigation tips and tricks!

 

[brucemacdonald]

Adi,

I have been interested in astronomy for over twenty years and I always use the first method of finding north.


But because the of the seasons and the fact that the Earth rotates once in 23 hours and 56 minutes, the Plough is not always aligned conveniently with Polaris directly above it.

As a quick guide, try the following at different times of year, in the evenings:

In the Summer, the Pointers (alpha and beta Ursae Majoris) will be to the LEFT of Polaris.

In the Autumn, the Pointers will be BELOW Polaris (as in the illustration).

In the Winter, the Pointers will be to the RIGHT of Polaris.

In the Spring, the Pointers will be ABOVE Polaris, ie the Plough will be upside-down and in the Zenith from UK latitudes (ie directly above you).

Best still is to learn some constellations and get into astronomy from a good dark site. It's just like any other form of Nature.

Best wishes,

Bruce

 

[woodsitter]

An elderly couple is sitting on a park bench at night, silently watching the stars. He slowly bends over to her and whispers:
“Do you want me to show you the Great Bear?”
She jumps ups and shouts: “You will not! You dirty old fool!"


(bit off topic, sorry )

 

[leon-1]

Yep ADI, you heard correctly about celestial navigation. You know how long can you can march on a star after you have taken a bearing on it (before that becomes inaccurate) and what the southern cross looks like.

The use of the sun to determine direction in all of the different methods that are out there (watch, long pole and stones).

If we have some sailors out there they may even be able to tell us how a sextant is used. :-D

 

[woodsitter]

O.k. to ad something a bit more useful, I am (a bit of) a sailor and I do know how a sextant works. But it’s not very Bushcraft!

A Sextant is a tool to measure the height of a star. If you have determined a star (so you know what star or system it is) and you also know where it should be (big books and charts) you can measure the position of the star in relation to the time and the horizon and therefore determine your position in relation to the star the horizon, the time and the big book with al the charts. (Does this make sense to anyone?) Well, the sextant is basically a gradient arch with lenses and mirrors. You hold it straight and look trough it, trying to find you star (or the sun). Then you move one of the mirrors to ‘drop’ the star onto the horizon (with should be flat, its originally a naval tool). The gradient arch now tell you how high the star is. In you book you now can find a line where you are. By shooting another star, knowing the exact time, shooting the sun or the moon, you can cross reverence and should be able to determine you position. By doing it regularly, plotting your position on a map and a log book, and keeping track of your speed and heading (compass) you can travel around the globe.

But a sextant is made of brass, very heavy and bulky, you also need your books, compass watch, maps, etc. Travelling on land is usually done by landmarks and maps, maybe a compass. Much easier and lighter. Even a five year old bulky GPS with six weeks of batteries is more handy then a sextant.

 

[TheViking]

Hi...

I always use Big Dipper! But this is only in emergency, and haven't had anyone of these, yet... Normally just carry my 2 £ watch compass.

 

[Adi007]

Here is the Southern Cross ... it can be used to find south in the Southern hemisphere:

Another one I use up here is the horns of the cresent moon ... trace a line to the horizon and you have a pointer to south.

 

[Douglas]

I used to be quite interested in astronomy too, but with time it faded away to more "down on earth" things, but I've still got all the star maps, the constallation cards, the binders full of stuff etc, etc, etc.

Another easy way is to find the little dipper, and it's "tail" star is Polaris. But since I got told the way of finding it from the big dipper (5 times the distance between A and B), that's what I use all the time. I never use it for navigation though.

Another of knowing your direction, that I read somewhere here, is:
-Mark a star, like indicating it's direction with sticks
-Come back 15 min. later, if the star has moved:
-Left : your facing north, or right: you're facing south
-Down : west, Up: Est

The sentance "Lost Nomads Die Wondering" can help you remember. (L = left, N = North ; D = down, W = West). Or otherwise just picture yourself the earth turning and how the stars move according to their direction.

Please, if I got it wrong, correct me, it would be silly to get lost because of that!

 

[leon-1]

Cheers woodsitter, I know that a sextant is used in the nautical world, and I thought that it would be of interest due to the fact that it is used for the Celestial Navigation side of life. I have never used one as you have probably gathered, but have always been interested in them, just curiosity really.

ADI, I have used all of the normal methods, but have never used the horns on the crescent moon, I'll have to have a look at that soon. Should be fun :biggthump

Marching on a star should only be done for a period of 15 minutes before you take a bearing on either another star or another object that will remain static, it was something that I learnt a long time ago

 

[leon-1]

Douglas another one that you can use is Never Eat Shredded Wheat.

If you use the N from never as being the top and then run clockwise with the rest you will get the four points of the compass. :wave:

 

[Adi007]

IAnother of knowing your direction, that I read somewhere here, is:
-Mark a star, like indicating it's direction with sticks
-Come back 15 min. later, if the star has moved:
-Left : your facing north, or right: you're facing south
-Down : west, Up: Est

The sentance "Lost Nomads Die Wondering" can help you remember. (L = left, N = North ; D = down, W = West). Or otherwise just picture yourself the earth turning and how the stars move according to their direction.

Please, if I got it wrong, correct me, it would be silly to get lost because of that!

Great way to remember it! Thanks Douglas! :biggthump

 

[Adi007]

Found this link on navigation ... http://www.w-o-w.com/ARTICLES/navigation/index.html

 

[Stuart]

when i was living in mauritius i spent a lot of time trying to navigate by the southern cross found it almost impossible!!!

there are so many stars in that part of the sky that could be a cross its difficult to locate the right one, even with a compass I had trouble finding it :?:

thankfully Orion comes to the rescue as he is visable on both sides of the equator and can be used as Adi describes to find the north/south line

 

[leon-1]

Great way to remember it! Thanks Douglas! :biggthump

Just a brief thing , but left of north is equal to west, and right is equal to east, I would defer,but i have been navigating with this stufff for years and it has been OK for this period of time :wave:

 

[Doc]

I've always admired sailors who can do celestial navigation with sextant, clock and almanac. Some argue it is a good backup in case the GPS fails, others claim that this is akin to keeping a horse in case your car won't start! Personally, I'm in favour of everything that relies more on skill and less on technology (like morse code, sailing, celestial nav and traditional archery).

Sextants are primarily for maritime use, though they can be used on land or for aviation with some form of artificial horizon (eg bubble or mercury)

If your compass has a clinometer you can get your rough latitude from measuring the angle between Polaris and the horizon. You'd be lucky to be closer than 2 degrees though, which if memory serves me correctly equates to 120 nautical miles of error - say a week's travel on foot!

 

[Seagull]

Guys, guys, guys.
Sextants, IMHO , are best veiwed on the walls of theme pubs.
I believe they have no place here.

As far as i know, the last time the hambone was used on land, was with the long range desert patrol group. In fact I,M sure they shifted over to theodelites in sharp order.

Maybe there are a few places where the droggies still use horizontal sextant angles, but I doubt it.

There were some marine sextants adapted for use without a visible horizon, these descended directly from the aero sextants, and had a bubble membrane.

Both types had a clockwork,wind-up averaging computer, for use with stars.
For sun shots, you made the bubble as near to the apparant size of the sun, and did your best to centre the image.
I still have aero type.
The computer ran for 2 mins ,dead, after which a shutter cut off the veiw.

Oy, I just realised I,m rambling-on.

But, if you really need to practise your brass-polishing techniques on the arc of a marine sextant, then please dont let a mariner see you doing it!

seagull

 

[Doc]

Well......all I know about the sextant for terrestrial navigation comes from reading about 19th century explorers!

Interesting how real (not the cheap and nasty brass Indian 'not for navigation' reproductions) sextants go for lots of cash on ebay. Probably bought as decoration?

Plastic 'lifeboat' sextants are not pretty but significantly cheaper.

The sextant is still in use with some recreational sailors I think - the 'lets just take a noonshot to check the GPS' mentality.

 

[Adi007]

The sextant is still in use with some recreational sailors I think - the 'lets just take a noonshot to check the GPS' mentality.

:rolmao: :rolmao: :rolmao:

 

[EdS]

I got given one of those plastic "lifeboat" sextants. I quite fancy having a go with it - just for the fun, but it I've no idea how to go about using it.

Anyone know here I can ge some instuctions?

 

[ChrisKavanaugh]

I was taught the sextant in the Coast Guard. I was told by a prominent british horseman that countless governess' carts, shooting breaks etc. were dusted off and became much needed transport during WW2, so never sell an old technology down the river. My service was a time of transition to electronics, G.P.S. and everything else that seems to play an electronic rendition of the japanese national anthem every 5 seconds in today's urban environment. I'm on the flying bridge shooting the stars with my Captain, an old time mariner who looked like Spencer Tracey and read Homer in greek. We had this new ltjg who, while competent, thought the new electronics the cat's meow. So we did our calculations, consulted the tables, looked solemnly at each other and nodded. The skipper turned to the ltjg and barked " second star on the right, then straight on till morning" turned on his heal and went to his cabin.