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#87858 - 03/09/07 07:27 AM celestial navigation
DLR Offline
Newbie

Registered: 01/01/07
Posts: 30
Loc: Phoeniz, AZ
Been layed up for a few day with a bum gut, I got to thinking. Anyone know how navigate with the stars and sun? I thought it'd be pretty cool to learn how to do this, but most everything I've googled has been pretty in-depth geek-speak that my hillbilly brain can't understand.

I know it isn't easy because if it was, we'd never have come up with a GPS. But civy GPS's can be spoofed, and compasses only tell direction.

Anyone got any ideas or other methods of determining specific Lat/Lon W/O maps or gps's? Anything you can recommend as a celestial navigation primer?

I would guess that a person wouldn't have the sextants or other equipment available all the time, but I still think it'd be cool to learn.

DLR

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#87863 - 03/09/07 01:46 PM Re: celestial navigation [Re: DLR]
RayW Offline
Addict

Registered: 12/06/01
Posts: 601
Loc: Orlando, FL
Here is a good place to start,

http://www.celestialnavigation.net/

But you may have already been there, but the knowledge still has uses today. Years ago the Coast Guard offered courses in celestial navigation. Friend of mine went through the course so that he could "hitch a ride" on sailboats he could not afford by offering his services as a back up to the GPS.

You might also look into orienteering,

http://www.4orienteering.com/

It might be possible to find a club in your area that can show you the way. HTH

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#87887 - 03/09/07 05:41 PM Re: celestial navigation [Re: NightHiker]
Coastie09 Offline
I didn't float test my chipping hammer, honest Chief!

Registered: 03/22/06
Posts: 104
Loc: Connecticut
I second Bowditch.

CelNav is can be difficult. I've had classes on it and know the theory, but putting that theory into practice is the hard part. The instructors don't tell you just how hard it is to aquire and maintain a sextant sighting on a pitching deck, when all the stars look nearly the same through the sight (you get tunnel vision and can lose the constellation).

Truely accurate Celestial Fixes require a perfect horizon, so anywhere other than the sea makes that difficult. Also, light pollution from cities, trees, and whathave you can all block the sky and make fixes that much harder. It's sad, but these days a lot of mariners just use GPS and have lost the art and science of CelNav because the electronic gizmos are faster, easier, and more accurate. I just hope an EMP or something won't render the world's maritime fleets useless.

If you are serious, PRACTICE, PRACTICE, PRACTICE. It requires a lot of gear that Night Hiker mentioned.

All that being said, I wouldn't get discouraged. CelNav is awesome and really cool to know. It would be great in a pinch, and the ladies like it when you can sit there and point out stars and constellations.

Matt

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#87891 - 03/09/07 06:23 PM Re: celestial navigation [Re: Coastie09]
Alex Offline
Old Hand

Registered: 03/01/07
Posts: 1034
Loc: -
I'm third smile

Though, it is possible to use an improvised measurement tools in the field (the perfect horizon line sight is optional and could be improvised too), plus an accurate watch (must have), the measurements+calculations precision would be somewhat frustrating (like +- 200 miles). Still not bad in trans-pacific plane crash situation...


Edited by Alex (03/09/07 06:25 PM)

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#87898 - 03/09/07 07:17 PM Re: celestial navigation [Re: Coastie09]
BlackSwan Offline


Registered: 12/05/06
Posts: 37
Quote:
how hard it is to aquire and maintain a sextant sighting on a pitching deck


I always wondered how someone gets an accurate angle of sun and horizon on a pitching deck.

For really amazing celestial navigation, I have always been fascinated by how the ancient polynesians did it. No sextant, compass or timepiece, yet they traveled thousands of miles of open ocean in large canoes. It is really a good read to see how they did it.

My sailor skills are nil, by the way.

Jeff

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#87907 - 03/09/07 07:52 PM Re: celestial navigation [Re: NightHiker]
Chris Kavanaugh Offline
Carpal Tunnel

Registered: 02/09/01
Posts: 3824
I was out one night with this Elder of the indian tribe I was working with. He was sharing the names and stories of each constellation and star. There was one moving slowly over our horizon I didn't recognise. I asked about it.< SIGH> that, Chris, is a communication satelite. Start out simple. Our own folklore teaches us that if nothing else. Heres two that always work for me; 'Follow the drinking gourd' used by escaped slaves to move north using the Big Dipper, and 'Second star on the right, then straight on till morning.'

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#87932 - 03/09/07 10:07 PM HillBilly to HillBilly [Re: DLR]
Micah513 Offline
Member

Registered: 07/18/06
Posts: 178
Loc: Springfield, MO
The following advice is coming from a redneck's perspective & isn't meant to be professional advice or taken too seriously. wink I'm not using the actual constellations names to keep it simple & would say start checking the night sky out now when you can be absolutely sure of where north.

The view of the night sky can be a challenge here in the sticks of the Ozarks. However, out where you're at this should be a piece of cake to get the general idea of where North is assuming you aren't clouded over.

One of the things that can instantly point me in the general direction of the North star is the moon. If the sun has just gone down or has only been down for a couple hours the side that is lit up white is west & if you draw a line thru the moon that line is pointing north & south.

On the moon itself (to my naked eye) there appears to be one finger pointing out of a hand which is pointing in the general direction of north. I first read that here
and have watched it over the last couple years & it is a ballpark truth - in other words it will get you started & then you have to find the north star using the following.

The Big Dipper. Asterik's are the stars. If you draw line thru the end of the cup it lines up with the North Star.

North Star ----->----->--*-
-----------------------------
--------*---*----------------
----*-----------*--------*---
-----------------------------
------------------*-----*----
-----------------------------


If the Big Dipper is below the horizon then there is another constellation that looks like a Giant "W" which is exactly opposite from the Bigger Dipper. This "W" is very funky so don't expect it to be perfect. The top of the "W" is pointing at the North Star as well - something similar to this. (Keep in mind I'm winging it from memory here :))

North Star ----->*----------
-----------------------------
-----------------------------
------*----------------------
----------------*---------*--
-----------------------------
------------*----------------
---------------------*-------


And last, but not least there is a partial Kite that moves across the night sky shapped something like this.

-----------North-------------
-----------------------------
-----------------------------
--------------*--------------
-----------------*-----------
--------------------*--------
-----------------------------
--------------*--------------
--------------*--------------
--------------*--------------

The stars at the top right angle of the kite are very bright & if they are in the sky then you can't miss them. This kite is also pointing north.

This is only meant as a quick & dirty description to get you started. Let me know if you have questions & if you go check it out what you find.

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#87933 - 03/09/07 10:14 PM Re: HillBilly to HillBilly [Re: Micah513]
Misanthrope Offline
Member

Registered: 09/08/05
Posts: 156
Loc: Chicago burbs
Excellent, succinct review of celestial nav.

Thanks.
_________________________
I hear voices....And they don't like you.

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#87935 - 03/09/07 10:18 PM Re: HillBilly to HillBilly [Re: Misanthrope]
Micah513 Offline
Member

Registered: 07/18/06
Posts: 178
Loc: Springfield, MO
Thanks, I was a little nervous about putting that out there, because there are some very smart, knowledgeable, technical & precise people on this board & what I described is a very basic view of how it looks to me standing out in my yard looking up.

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#87936 - 03/09/07 10:26 PM Re: HillBilly to HillBilly [Re: Micah513]
Misanthrope Offline
Member

Registered: 09/08/05
Posts: 156
Loc: Chicago burbs
And that's exactly how it is going to look to somebody in the bush. Which is the whole point.

Again, Thanks.

_________________________
I hear voices....And they don't like you.

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#87944 - 03/10/07 12:46 AM Re: HillBilly to HillBilly [Re: Micah513]
JCWohlschlag Offline
Old Hand

Registered: 11/26/06
Posts: 724
Loc: Sterling, Virginia, United Sta...
Thanks for posting that! I’ve always enjoyed looking up at the night sky and learning about the constellations. In fact, I’ve had a great time using a program I found called Stellarium which can basically paint a picture of what your sky should look like from any point on Earth at any date or time.

I would like to ask you if you can give any more details about the third method you posted. I am familiar with the first method, using Ursa Major (the Big Dipper), and I am familiar with Cassiopeia (the ‘W’). I am not familiar with your “kite” however, and I cannot seem to figure out which constellations/stars you’re looking at.
_________________________
“Hiking is just walking where it’s okay to pee. Sometimes old people hike by mistake.” — Demitri Martin

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#87947 - 03/10/07 02:41 AM Re: HillBilly to HillBilly [Re: JCWohlschlag]
DLR Offline
Newbie

Registered: 01/01/07
Posts: 30
Loc: Phoeniz, AZ
AARRGGHH..My head hurts.

Who knew that it was so involved simply to pinpoint your exact position on a rotating sphere hurtling through space??

I love my gps even more now...


DLR

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#87954 - 03/10/07 04:37 AM Re: HillBilly to HillBilly [Re: Micah513]
Blast Offline
INTERCEPTOR
Carpal Tunnel

Registered: 07/15/02
Posts: 3760
Loc: TX
Dude, that was beautiful!

To add my own two cents, here is a link to an easy to make "star clock". It'll tell you what time it is if you can see the stars. Conversly, if you know what time it is you can use it to find the stars (hint: look up grin). Someday I'm going to make a tiny one that I can hang around my neck.

Star Clock

-Blast
_________________________
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*As an Amazon Influencer, I may earn a sales commission on Amazon links in my posts.

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#87960 - 03/10/07 05:13 AM Re: celestial navigation [Re: DLR]
wildman800 Offline
Carpal Tunnel

Registered: 11/09/06
Posts: 2847
Loc: La-USA
CelNav is a subject that is near and dear to my heart. Yes, I have navigated by celnav at sea.
1st, a disclaimer, I had to learn celnav in order to make QM1 (E-6) in the USCG. The problem that I encountered (and so has most every other person), reading the theory does nothing to help you translate theory into the practical art of finding your location. I (and most others), had someone who was knowledgable, walk us through the first 3 fixes and then left us on our own. After you have laid down the tenth fix (or thereabouts), SUDDENLY, the light bulb goes off, and you now understand what all that gobbleygook theory was trying to tell you!!!!!!
I recommend "The American Practical Navigator" by Nathaniel Bowditch as far as trying to learn the theory and the steps required to ascertain a position.
The best way is still to set sail and have someone walk you through the process, the pubs required, and the charting. 20 mile accuracy is acceptable for celnav (I actually maintained a 5 mile accuracy), for sun lines and star plots.
If you learn how to work out a position, be ready to experience a very strong MENTAL orgasm, That's the only way I can describe the feeling that I get when I do a good fix!
_________________________
QMC, USCG (Ret)
The best luck is what you make yourself!

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#87962 - 03/10/07 05:18 AM Re: HillBilly to HillBilly [Re: NightHiker]
wildman800 Offline
Carpal Tunnel

Registered: 11/09/06
Posts: 2847
Loc: La-USA
The "kite" that he is talking about is, My guess, Scorpio.

Just as the Big Dipper lets you find the North Star, The scabbard on Orion's belt, always points South
_________________________
QMC, USCG (Ret)
The best luck is what you make yourself!

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#87968 - 03/10/07 07:42 AM Re: HillBilly to HillBilly [Re: Micah513]
redflare Offline
Addict

Registered: 12/25/05
Posts: 647
Loc: SF Bay Area, CA
Thanks Micah,

Just the kind of barebones info I was looking for. Printing out now. smile

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#87970 - 03/10/07 09:19 AM Re: HillBilly to HillBilly [Re: wildman800]
JCWohlschlag Offline
Old Hand

Registered: 11/26/06
Posts: 724
Loc: Sterling, Virginia, United Sta...
Originally Posted By: wildman800
The "kite" that he is talking about is, My guess, Scorpio.

Thank you for that! It does appear that three stars in the “tail” (&#950;2, &#956;1 [Denebakrab], and &#949; [Wei]) appear to point to Polaris while three stars in the “claws” (&#960; [Vrischika], &#948; [Dschubba], and &#946;1 [Acrab]) appear to make the diagonal line in front. Good catch!
_________________________
“Hiking is just walking where it’s okay to pee. Sometimes old people hike by mistake.” — Demitri Martin

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#87981 - 03/10/07 10:22 PM Re: HillBilly to HillBilly [Re: JCWohlschlag]
wildman800 Offline
Carpal Tunnel

Registered: 11/09/06
Posts: 2847
Loc: La-USA
Another constellation in the northern sky that also looks like a kite is: Cygnus, the swan. Come to think of it, that's what he is most likely talking about.
_________________________
QMC, USCG (Ret)
The best luck is what you make yourself!

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#87982 - 03/10/07 11:54 PM Re: HillBilly to HillBilly [Re: redflare]
Alex Offline
Old Hand

Registered: 03/01/07
Posts: 1034
Loc: -
Hmm. I don't know what "kite" is representing either, despite of my 25 years of amateur astronomy experience, and 100% knowledge of the night sky smile It's not Scorpio or Orion, for sure. Most likely a combination of several constellations. I'm very intrigued, what is that?

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#87983 - 03/11/07 12:04 AM Re: HillBilly to HillBilly [Re: wildman800]
Alex Offline
Old Hand

Registered: 03/01/07
Posts: 1034
Loc: -
Originally Posted By: wildman800
...Cygnus, the swan...

But where is the Deneb and Vega then? The brightest stars near that place? If Deneb is the topmost star in the "kite" then the bottom star is Eta Cygnus, it's way too faint. It doesn't have even a proper name.


Edited by Alex (03/11/07 12:13 AM)

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#87987 - 03/11/07 12:58 AM Re: HillBilly to HillBilly [Re: wildman800]
JCWohlschlag Offline
Old Hand

Registered: 11/26/06
Posts: 724
Loc: Sterling, Virginia, United Sta...
I cannot find star sets in or around Cygnus that would resemble the ASCII art provided. I have included a Stellarium screenshot of that area of the sky for reference.

_________________________
“Hiking is just walking where it’s okay to pee. Sometimes old people hike by mistake.” — Demitri Martin

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#87991 - 03/11/07 01:44 AM Re: celestial navigation [Re: DLR]
wildman800 Offline
Carpal Tunnel

Registered: 11/09/06
Posts: 2847
Loc: La-USA
Another thing that my slow moving brain just received from the Archive Databank - I bought a star chart at the local bookstore (national chain type) that is very easy to use and has the stars of each constellation linked together. It's very easy to use and I have enjoyed mine immensely!

Remember, senility sucks!!!
_________________________
QMC, USCG (Ret)
The best luck is what you make yourself!

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#87994 - 03/11/07 02:25 AM Re: celestial navigation [Re: wildman800]
Alex Offline
Old Hand

Registered: 03/01/07
Posts: 1034
Loc: -
As a piece of the survival gear I'd recommend this kind of charts: http://www.lawrencehallofscience.org/StarClock/skywheel.html

(Thanks to Blast for the site). This chart could be used as the best Polaris finder, star clock, calendar and compass (at night of course).


Edited by Alex (03/11/07 02:26 AM)

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#87996 - 03/11/07 02:49 AM Re: celestial navigation [Re: Alex]
wildman800 Offline
Carpal Tunnel

Registered: 11/09/06
Posts: 2847
Loc: La-USA
That is basically the same chart that I was talking about in my earlier post.
_________________________
QMC, USCG (Ret)
The best luck is what you make yourself!

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#88039 - 03/11/07 08:15 PM Re: HillBilly to HillBilly [Re: Alex]
Micah513 Offline
Member

Registered: 07/18/06
Posts: 178
Loc: Springfield, MO
The partial kite (or at least what my brain perceives as a partial kite) is Orion's Belt & Sword. It is a couple degrees off from true north and I didn't do a very good job of drawing it up from memory as I got it backwards, but keep in my I said this was coming from a Hillbilly's perspective & off the top of my head from memory which is fading in my old age crazy
And if I was out in the brush & looked up into the sky I would still pick it out right away.

Here is probably closer to what I should have posted. I do know the tail is kind of a fuzzy glow of several stars to the naked eye.


-----------North-------------
-----------------------------
-----------------------------
--------------*--------------
----------*------------------
------*--------------*-------
-----------------------------
-----------------------------
-------------*---------------
--------------*--------------
--------------*--------------


Here is another image Belt & Sword

Or better yet go to Google. Type in "Orion's belt" and click on images. There are some cool ones out there. The belt is so bright that even if it is hazy sky it is still findable.



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#88041 - 03/11/07 09:00 PM Re: HillBilly to HillBilly [Re: Micah513]
Alex Offline
Old Hand

Registered: 03/01/07
Posts: 1034
Loc: -
Well, the Orion's belt is exactly on the equator of the celestial sphere. So it's 90 deg. off the Polaris. Also the size of the "dagger" (which is really pointing to Polaris) is so tiny - you can cover it with your thumb. I doubt it's a good guide to Polaris. It's more like an indicator to look into opposite direction for Big Dipper or Cassiopeia.


Edited by Alex (03/11/07 09:02 PM)

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#88054 - 03/11/07 10:53 PM Re: HillBilly to HillBilly [Re: Alex]
Micah513 Offline
Member

Registered: 07/18/06
Posts: 178
Loc: Springfield, MO
I can spot Orion's belt very quickly & then I'm off to the races. Overall it may not be the best tool to use, but works for me.

Do you have other recommendations for us amateurs?

(Pointing me to a website that has a thousand stars & hundreds of connecting lines running every which way isn't going to help me when I need to find Polaris quickly)

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#88057 - 03/11/07 11:21 PM Re: celestial navigation [Re: DLR]
Anonymous
Unregistered


Navigation using the stars is actually reasonable simple and it very simple to get a Latitude position and with a reasonable degree of accuracy. Longitude measurement is slightly more difficult.

Firstly find the star called Polaris. Polaris is easy to find. Polaris always points north if you are in the northern hemisphere. Get your compass out from your PSK and look upwards in the northerly direction. In the northern hemisphere all the other stars rotate around Polaris over the course of the night. A quicker method is to find Ursa Major (Great Bear or as in the UK referred to as the Plough) and then locate the star Merak (the front corner of the plough's blade). In this constellation the nearest brightest star will be Dubhe. Follow the imaginary line these two stars make and here you find the next brightest star in sequence called Polaris. Merak and Dubhe will point to the star Polaris. Once you know how to find the star Polaris using this method you don't even need a compass to start off with.

Secondly to determine you Latitude you just measure then angle or angular separation between the horizon and the star Polaris. To do this you need a sextant. Point the telescope viewer or iron sight of the sextant at the star Polaris and read of the angle. This is your Latitude.
Even a simple bush craft made sextant will get you within + or - 100 miles approximately either way of your true Latitude. A bubble indicator from a spirit level is always handy to have in your PSK together with your hacksaw blade. The bubble indicator will allow the bush craft sextant to be level with the horizon if the horizon is difficult to determine in the dark. The hack saw blade will allow you mark of the ratios of 3,4,5 so as to give you a right angle triangle, which will then give an accurate angular reference measurements of 36.87 and 53.13 degrees. These reference angles can then be accurately subdivided into smaller angles and will allow the construction of a reasonably accurate bush craft sextant. Achievable accuracy could be + or – 1 degrees.

Since accurate time and global navigation were invented in Britain due of the invention of the chronometer or pocket watch by Harrison (Known as H4) in the late 17th century, the reference angle of 0 and 360 degrees is set to the imaginary north south line called the prime meridian which bisects the globe through Greenwich in London.

Longitude is much more difficult to determine as this will require an accurate timepiece, which is set to Greenwich Mean Time or is at least referenced to Greenwich Mean Time GMT or UTC (otherwise known as Universal Time Co-ordinate) and something called a solar ephemeris table.
By measuring the referenced time of the sunrise and sunset together with the time of year and the measured latitude then by looking up the solar ephemeris table a reasonable measurement of latitude can be derived.
Generally having an accurate timepiece is not really a problem especially with today’s modern quartz regulated watches. (It may surprise some that the British Harrison H4 which is over 250 years old will actually keep better time than most contemporary Japanese and Swiss timepieces). Having a solar ephemeris table is not something that most people would have access to in the wilderness.

A simpler less accurate method is to measure the time of the suns zenith (the point at which the sun is the highest in the sky at the longitude to be determined). This can be done using a bush craft sundial. Improved accuracy can be achieved by the use of averaging the time of the each daily sun’s zenith time results.

1 day’s rotation of earth = 360 degrees = 24 hours
15 degrees = 1 hour
1 degree = 1/15th hour = 4 minutes (this will be accurate to again + or – 60 miles approximately)

Measuring the difference in time between local noon and Greenwich noon made it possible to determine longitude. If local noon was 6 hours after Greenwich noon, the latitude will be 90 degrees (6* 15) west of Greenwich.
Because the earth rotates once per day, any given point on the earth's surface travels through a circle of 360 degrees once every 24 hours. Thus, each hour, a given point travels through 15 degrees of longitude (360/24). To determine one's longitude, one compares the time of local noon (when the sun is at its highest point) to the time of noon at a place with a known longitude. The difference in time is converted to the difference in longitude with a fairly simple calculation.
For example, if one hour is equal to 15 degrees, then 6 hours would equal 90 degrees, and 6 hours and 30 minutes would be 97.5 degrees.
If the local sun’s zenith can be fixed within 4 minutes then the location of the longitude to be measured will be between + or – 60 miles approximately of the true longitude.




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#88059 - 03/11/07 11:30 PM Re: HillBilly to HillBilly [Re: Alex]
ironraven Offline
Cranky Geek
Carpal Tunnel

Registered: 09/08/05
Posts: 4642
Loc: Vermont
It gives east-west pretty reliably. Put it to your back, and you are looking north-ish, and you can start looking for other landmarks. (skymarks?)
_________________________
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When a man dare not speak without malice for fear of giving insult, that is when truth starts to die. Truth is the truest freedom.

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#88060 - 03/11/07 11:57 PM Re: HillBilly to HillBilly [Re: ]
Micah513 Offline
Member

Registered: 07/18/06
Posts: 178
Loc: Springfield, MO
Piece of cake!

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#88061 - 03/12/07 12:08 AM Re: HillBilly to HillBilly [Re: Micah513]
raydarkhorse Offline
Addict

Registered: 01/27/07
Posts: 510
Loc: on the road 10-11 months out o...
Most stores that sell telescopes sell a map of the stars that show you the night sky, it's adjustable to the time and date. It is round made of plastic and weighs about 1oz I keep one in my pack with my compass.
_________________________
Depend on yourself, help those who are not able, and teach those that are.

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#88063 - 03/12/07 12:24 AM Re: HillBilly to HillBilly [Re: Micah513]
Alex Offline
Old Hand

Registered: 03/01/07
Posts: 1034
Loc: -
Originally Posted By: Micah513
Do you have other recommendations for us amateurs?

I'm just arguing against the Orion (kite) method cool, which might lead you to nowhere. The other two, which was very well described by Micah513, are sufficient enough. Though, the starchart is the best tool if you happen to have an obscured sky view (forest, hills, clouds, window...).

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#88106 - 03/12/07 02:29 PM Re: HillBilly to HillBilly [Re: Alex]
Micah513 Offline
Member

Registered: 07/18/06
Posts: 178
Loc: Springfield, MO
Originally Posted By: Alex
I'm just arguing against the Orion (kite) method


I really wanted to check this out further, because I sure don't want to mislead anyone. I went outside last night & we were mostly clouded over. Could not make out any stars at all in the North or South, but there was a band straight up & to the west where the clouds were thinned out. In the middle of that thin band was Orion's belt. It was very easy to make out because the less bright stars are all drowned out. The kite is pointing about 10 degree's off of true north towards the west.

So you definitely don't want to follow this constellation (unless you want to go NNW grin) as true north. However, the top of the kite does point northward & Orion's sword definitely points southward & I will still use this so I can quickly get my general directions down. Then move onto the other constellations (Cassiopeia & Ursa Major) to get a more precise true north.

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#88161 - 03/12/07 11:05 PM Re: HillBilly to HillBilly [Re: Micah513]
dougwalkabout Offline
Crazy Canuck
Carpal Tunnel

Registered: 02/03/07
Posts: 3222
Loc: Alberta, Canada
I guess "navigate" needs to be defined.

If you mean "navigate in terms of lattitude and longitude," that's a tall order. It requires knowledge, practice, equipment and reference materials to do effectively.

But if you mean "orient yourself and move in the right direction by dead reckoning," that's another thing entirely.

Anyone can learn to find the North Star (Polaris) on a clear night.

And, anyone can get a very crude east/west line during a sunlit day, using the "stick and shadow" method. But: in my limited experience, this is not exact, so it's best to experiment in your lattitude and figure out the error factor. I suspect the error increases as your lattitude increases (i.e., going north).

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#88215 - 03/13/07 08:46 AM Re: celestial navigation [Re: Coastie09]
jamesraykenney Offline
Enthusiast

Registered: 03/12/04
Posts: 316
Loc: Beaumont, TX USA
Originally Posted By: Coastie09
<snip>
Truely accurate Celestial Fixes require a perfect horizon, so anywhere other than the sea makes that difficult.
<snip>


Problem... No horizon visible on land...
Answer... Artificial horizon.
About $23.00 for a cheap plastic one that uses water for the reflector



to who knows how much for a mercury one like THIS ...

I only have one of the plastic ones...


Edited by jamesraykenney (03/13/07 08:48 AM)

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#88232 - 03/13/07 03:33 PM Re: celestial navigation [Re: jamesraykenney]
Alex Offline
Old Hand

Registered: 03/01/07
Posts: 1034
Loc: -
Nice find! But for the survival purposes a simple improvised plumb-line (a rope with weight) is precise enough. And the measurements are less complicated with it. The longer the rope the higher the precision. In fact, the real horizon line is a necessity for the rocking ship situation only (I doubt the artificial one would work on the ship well). If absolutely necessary, an inexpensive bubble level would give you about 1 minute precision (1/60th of a degree), what's more than enough for visual measurements, which theoretically allows to determine your location with ~1mile precision.


Edited by Alex (03/13/07 04:51 PM)

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My Doug Ritter Folder Attacked Me!
by dougwalkabout
05/04/24 02:30 AM
Bird Flu (H5N1) found in cattle -- are Humans next
by dougwalkabout
04/29/24 04:00 AM
People Are Not Paying Attention
by Bingley
04/28/24 03:24 AM
Corny Jokes
by wildman800
04/24/24 10:40 AM
USCG rescue fishermen frm deserted island
by brandtb
04/17/24 11:35 PM
Silver
by brandtb
04/16/24 10:32 PM
EDC Reduction
by Jeanette_Isabelle
04/16/24 03:13 PM
New York Earthquake
by chaosmagnet
04/09/24 12:27 PM
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