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Old 24-02-2013, 17:43   #31
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Re: Self Taught Celestial

Some helpful comments here, some not so much. Not sure I understand how learning celesstial navigation techniques is in any way detrimental to good seamanship. It is an interesting exercise that may prove necessary some day. And I fully embrace the use of GPS and modern navigational tools, as I already make good use of them.

After a few days of overcast weather, I was finally able to take some sights via an artificial horizon. Here's what I got for some initial sextant readings on my driveway:

UTC Time / Height
18:04:45/ 39 Deg 29.8'
18:49:01 / 37 Deg 52.8'

I'll work out these on a plotting sheet to see how close it comes to my true position of 41 Deg 45' N / 86 Deg 50' W. If others care to work these out, please post.
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Old 24-02-2013, 18:17   #32
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Re: Self Taught Celestial

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Originally Posted by Teknav View Post
Teknav's celestial navigation made easy... Look up Garmin.com ! Buy a portable/pocket GPS. Turn ON the GPS and wait a few seconds for a bunch of satellites to show up on your screen...and presto...you've got your Longitude and your Latitude; in degrees, minutes and seconds, of course...ummm +/- 25 ft, accuracy for el-cheapo pocket GPS. <Save your money by not buying a sextant! But if you are still determined to buy a sextant, you also need to buy an abacus and a slide rule to complete the set.> Mauritz
I think you are missing the point of the OP. We all have GPS's. It's just nice to learn an old art of navigation

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Hello Monster! Here's a different way to approximately confirm where you are at, while sailing. Pilots who fly IFR (following Instrument Flight Rules), must communicate specific positions, when they are reached, to air traffic control centers. These positions are marked on flight charts as "radial fixes - solid triangles markings on some charts" transmitted from land-based navigational beacons; VOR's (Very High Frequency Omni Range Radio). You can superimpose these positions on a navigational charts using their longitude and latitude. You will not be able to listen to the Morse identifier codes for VOR's or for air traffic controllers, because of line of sight transmission limitations. You should, however, be able to listen to IFR pilots overflying and confirming these mandatory fixes, as they have names; an air band scanner is good enough to hear the one-sided communication, thus re-confirming the proximity of your position. <Much more fun, than using a sextant.> Mauritz
...on second thought...maybe your GPS is not working all that well...You're an aircraft enthusiast that has navigated into a sailing forum.
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Old 24-02-2013, 18:39   #33
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Re: Self Taught Celestial

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Originally Posted by PCFithian View Post
After a few days of overcast weather, I was finally able to take some sights via an artificial horizon. Here's what I got for some initial sextant readings on my driveway:

UTC Time / Height
18:04:45/ 39 Deg 29.8'
18:49:01 / 37 Deg 52.8'

I'll work out these on a plotting sheet to see how close it comes to my true position of 41 Deg 45' N / 86 Deg 50' W. If others care to work these out, please post.
according my calculation (from Europe) Mer. Pass. on your Lat/Long is 18:00:19 UTC, bit late for noon sight, for sun run sun, sights are to close, at least one hour before noon and one hour after noon.

here you have almanac and correction tables for free.

http://navsoft.com/downloads.html
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Old 24-02-2013, 18:39   #34
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Re: Self Taught Celestial

Wise sailors learn celestial for the same reason parachutists carry a reserve chute and for the same reason we have life rafts. The Titanic was "unsinkable" so it never had enough lifeboats. What makes some people 100% certain that GPS will never go down for civilians?

Maybe remove those bilge pumps, thru hull shut off valves, first aid kits, fire extinguishers, life jackets, safety harnesses and gybe preventers if one is going to live by the same nothing bad can happen to me philosophy? At least that would be consistent.

Are some of you sure you only want to have one way of fixing your position when other methods are available?
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Old 24-02-2013, 18:56   #35
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Wise sailors learn celestial for the same reason parachutists carry a reserve chute ...
So ... how soon does certain death come after GPS and DR failure?

I carry a plastic sextant, almanac, clock and know how to do the calculations but am confident I will never use them even with total GPS failure.
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Old 24-02-2013, 19:17   #36
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Re: Self Taught Celestial

Hey Qantas flying above my boat, if you're listening to channel 9...what is your 10-20? That's a 10-4! Mauritz
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Old 24-02-2013, 19:25   #37
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Re: Self Taught Celestial

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Originally Posted by David M View Post
Wise sailors learn celestial for the same reason parachutists carry a reserve chute and for the same reason we have life rafts. The Titanic was "unsinkable" so it never had enough lifeboats. What makes some people 100% certain that GPS will never go down for civilians?

Maybe remove those bilge pumps, thru hull shut off valves, first aid kits, fire extinguishers, life jackets, safety harnesses and gybe preventers if one is going to live by the same nothing bad can happen to me philosophy? At least that would be consistent.

Are some of you sure you only want to have one way of fixing your position when other methods are available?
All good points. This is a revisit of a thread a few days ago. Unfortunately these threads end up much the same as the anchor or Mono vs Cat threads do.
In the news recently has been a pile of hub bub regarding cyber attacks from the Chinese. A virus uploaded into the GPS satellites would stop them dead. I use to laugh at people who told me .."What if those satellites go down". But after hearing it on the news, I'm not laughing anymore.
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Old 25-02-2013, 02:53   #38
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Re: Self Taught Celestial

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Hey Qantas flying above my boat, if you're listening to channel 9...what is your 10-20? That's a 10-4! Mauritz
Quantas is probably monitoring his VHF AM on 123.45 and 121.5 if he is under Oceanic Control. His set doesn't go up to 156.45 (Ch 9) and does not work with marine FM signals. Now if you get on your SSB you might find him on an HF frequency, but he is probably monitoring SELCAL!
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Old 25-02-2013, 04:03   #39
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Re: Self Taught Celestial

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What makes some people 100% certain that GPS will never go down for civilians?
If or when it does, I suspect the last thing you'll be worried about it where you are.

( and of course in a few years taking GPS,GLONASS, GALLileo, etc down as well).


Celestial is never justified by saying its a backup to GPS, Its just a fun thing to learn, thats all the justification thats needed.

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Old 25-02-2013, 04:58   #40
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Re: Self Taught Celestial

I think the chance that the will be a power issue on board would be greater than the satellite system(s) going down.

Take a good supply of batteries for the handheld and you can still have fun taking cel shots
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Old 25-02-2013, 05:47   #41
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Re: Self Taught Celestial

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A virus uploaded into the GPS satellites would stop them dead. I use to laugh at people who told me .."What if those satellites go down". But after hearing it on the news, I'm not laughing anymore.

It took the combined efforts of the NSA, the Israelis and Siemens ( the makers of teh PLC in question) to load a 'virius' into it to shake the centrifuges to bits in Iran, in that they delayed them for about 40 days.

If someone loads a virus into a GPS satellite, firstly a large number of people are going to get fired in a certain underground bunker. and secondly since each satellite is independent they would have to affect all of them ( and then what about GLONASS).

Seriously a bus will drop on you head first, yet I dont see you building battle armour to handle that!!!..

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Old 25-02-2013, 08:51   #42
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Re: Self Taught Celestial

i got this.....

noon sight




sun sights.....




and ploting sheet

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Old 25-02-2013, 08:58   #43
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Re: Self Taught Celestial

could I suggest a workbook approach for the calculations, it keeps things nice and ordered

as to the sun sights , have you plotted a running fix, I cant make it out, The lines of position are too close together in time to be of much use as the angle is too small for good accuracy, but other then that it looks great ( given what I can make out )
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Old 25-02-2013, 09:29   #44
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Re: Self Taught Celestial

Scimitar, I greatly appreciate your work on this. However, I 'm not sure I understand your progression with the the corrections and determinations from there.

Can you explain a bit further?
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Old 25-02-2013, 10:20   #45
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Re: Self Taught Celestial

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Wise sailors learn celestial for the same reason parachutists carry a reserve chute and for the same reason we have life rafts.
Not being wise or a parachutist I have a sextant onboard mainly because it's fun and gives a certain feeling for the boats spot on an ocean in relation to the rest of the universe, much more than staring at a some numbers on a screen.

The new opencpn celestial nav plug in looks promising for anyone wanting to have a play around just taking sights rather than the whole calc hog every time, sometimes easier breaking the process up a bit when learning...

Celestial Navigation Plugin Redux
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