The New and Improved Celestial Navigation Poll

[s/v Jedi]

Originally Posted by sneuman

Fine, I concede your point. What I don't get is how to rationalize your two statements:

a) CN is not accurate enough for Nav among the Pacific atolls (i.e., so why bother with CN) ... and ...
b) Why bother with CN when an iPhone will do everything for you, albeit less accurately than a sextant.

That's what I mean by "you can't have it both ways."

That point a) was in response to somebody that told to take a sextant for Pacific crossings only. It is the context that gets lost along the way.

Point b) you still don't get... try it again: the iPhone will become a sextant with that app. So it doesn't replace CN.. you just use an iPhone instead of a sextant. Think of it physically you point the iPhone at the stars and align the edge of the phone must like you would do the barrel of a gun. The sensors will show the angle on screen, instead of on the scale of a sextant.

For emergencies I keep to my point that a compass is all that is needed to save ourselves, as it will bring us very close to our planned destination when GPS stops working halfway. Often, we would know compass heading to closer destinations too.

A sextant in good practiced hands can replace a GPS chartplotter. Every navigator that use(d) a sextant would use a compass as backup. This leads to my logical conclusion that compass is a good backup to GPS too.

ciao!
Nick.

[sneuman]

Originally Posted by s/v Jedi

That point a) was in response to somebody that told to take a sextant for Pacific crossings only. It is the context that gets lost along the way.

Point b) you still don't get... try it again: the iPhone will become a sextant with that app. So it doesn't replace CN.. you just use an iPhone instead of a sextant. Think of it physically you point the iPhone at the stars and align the edge of the phone must like you would do the barrel of a gun. The sensors will show the angle on screen, instead of on the scale of a sextant.

For emergencies I keep to my point that a compass is all that is needed to save ourselves, as it will bring us very close to our planned destination when GPS stops working halfway. Often, we would know compass heading to closer destinations too.

A sextant in good practiced hands can replace a GPS chartplotter. Every navigator that use(d) a sextant would use a compass as backup. This leads to my logical conclusion that compass is a good backup to GPS too.

ciao!
Nick.

So, what kind of accuracy does that get you?

[s/v Jedi]

Originally Posted by sneuman

So, what kind of accuracy does that get you?

I never tied it but think that somebody who is skilled with a real sextant will get decent results while beginners won't have a clue. I only once or twice got a fix within 1 nm of GPS position (using real sextant) so I'm bad anyway because old salts tell me they are within 0.5nm every time...

ciao!
Nick.

[Astrid]

One nautical mile is not bad Nick, up to two is acceptable. A skilled operator using a top of the line sextant from a fairly steady ship can get within .25nm, but most of us on a small boat will be lucky to get within 1nm.

[s/v Jedi]

Originally Posted by Astrid

One nautical mile is not bad Nick, up to two is acceptable. A skilled operator using a top of the line sextant from a fairly steady ship can get within .25nm, but most of us on a small boat will be lucky to get within 1nm.

Well.. I said I managed that only once or twice

But I always got around that 1.4-1.5 nm which was considered okay'ish. I remember that I tried a plastic sextant once (those green things) and got within 1 nm first and only try. Walked away like I was the expert but had a hard time not laughing because it was my best fix ever in other words: pure luck or flair or whatever was at work that day

ciao!
Nick.

[sneuman]

Originally Posted by s/v Jedi

I never tied it but think that somebody who is skilled with a real sextant will get decent results while beginners won't have a clue. I only once or twice got a fix within 1 nm of GPS position (using real sextant) so I'm bad anyway because old salts tell me they are within 0.5nm every time...

ciao!
Nick.

1nm is quite good, actually. But your statement begs the question, if it takes someone "skilled with a real sextant" why not just use a real sextant? For anyone else, the iPhone is not going to be much use, anyway.

[s/v Jedi]

Originally Posted by sneuman

1nm is quite good, actually. But your statement begs the question, if it takes someone "skilled with a real sextant" why not just use a real sextant? For anyone else, the iPhone is not going to be much use, anyway.

Not for you, but many have the iPhone already and use it for everything. Remember, any tool in your pocket is better than one out of reach.

Siri?

Plonk! Yes Nick?

Remind me to practice using you as a sextant tomorrow...

What time do you want me to remind you?

At sunrise, Siri.

Okay Nick, I'll remind you.


ciao!
Nick.

[sneuman]

Originally Posted by s/v Jedi

Not for you, but many have the iPhone already and use it for everything. Remember, any tool in your pocket is better than one out of reach.

Siri?

Plonk! Yes Nick?

Remind me to practice using you as a sextant tomorrow...

What time do you want me to remind you?

At sunrise, Siri.

Okay Nick, I'll remind you.


ciao!
Nick.

Well, OK. Let's shake hands. Like I said, this is a minor point of disagreement between you and me.

It seems I managed to make at least one CF enemy today by asking a simple question, so no need to belabor this.

[deckofficer]

Originally Posted by sneuman

Well, OK. Let's shake hands. Like I said, this is a minor point of disagreement between you and me.

It seems I managed to make at least one CF enemy today by asking a simple question, so no need to belabor this.

No such thing as a CF enemy. I have a few that don't understand me, that might be the case for you.

No enemies here, just not all on the same wavelength.

[Ex-Calif]

If one still has the iPhone working after the lightning strike one needn't use it as a sextant. It is a gps plotter.

Tempest in a teapot.

CN is an interesting and useful skill. Many have stated they will learn it after the docklines are cast and timeis more available. I am in that crowd. Just understanding the night stars is a cool thing anyway.

In the meantime, "there's an app for that!"

[moira]

I don't understand the first selection in the poll. An almanac and a copy of HO 211 isn't much to carry on a vessel.

[Nemo55]

qiyas
Before the invention of the compass, watch, and the sextant, the mariner's main guide was latitude. To obtain their latitude, Arabs measured the altitude above the horizon to a known star, and then deduced from this the altitude of the Pole Star, (since the Pole Star was the one star that did not move in the sky). In some cases ancient navigators measured directly the altitude of the Pole Star. This was the simplest method, and was known as the science of qiyas. The easiest method was to use the width of a finger. When held at arm's length, the width of four fingers was considered to measure 4 isba'. In a 360 degree circle there were 224 isba'. It was considered that a day's sailing due north would raise the Pole Star 1 isba' from the horizon. For those traveling on land, the isba' was further divided into 8 zam. Thus land distances were often measured in zams.

kamal
A more accurate, but still simple instrument was known as a kamal. This was a small parallelogram of horn or wood measuring about one by two inches with a string inserted in the center. On the string were nine knots at measured intervals.
The end of the string was held in the teeth. The lower edge of the horn was placed on the horizon while the horn was moved along the string until the upper edge touched the required star. The knot at which the horn covered the exact distance signified a certain number of isba' of altitude of the star. The altitude of the Pole Star could then be deduced from the rahmani.
An alternative way of using a kamal was to move the knots through the teeth until the piece of horn or wood covered the required star altitude.
Vasco da Gama's pilot from Malindi used a kamal, and the Portuguese adopted it and eventually modified the spacing of the knots to measure degrees.
Sometimes Arab and Indian seamen added extra knots marking the latitudes of particular ports of call, or they simply used a kamal on which all the knots indicated particular ports of call.

[red_sky]

@nemo55 that is very cool. didn't know about that one. thanks for posting!

I have to change my answer to the last option now. My Tamaya arrived the other day, w00t!

[moira]

Then shortly after you pull your last remaining GPS out and put it in service it gets soaked, dropped orver the side, or one of the many two cent Chinese diodes in its innards gives up the ghost.

[Jonathan Reiter]

Could I say this without being attacked? Probably not, but here goes anyway. First off, those cheap plastic sextants are perfectly usable for sun sights as thousands of passage makers will attest to. A noon sight every few days will correct any wandering from your DR on a crossing. I had a Magnavox transat unit ( same as on the supertankers I worked on) in the '80s, and on the crossing from Tenneriffe to Antigua, it was so boring knowing EXACTLY where we were 24/7, that I would turn it off 23 hours a day. In the early '90s, I made a bet that I could sail from the west coast to Hilo with only a compass and an AM receiver. I left Cabo, and 26 days later, raised the big island. My landfall was 12 miles off Radio Bay. (This is where the attacks will start.) Last, there has been available for many moons a handheld calculator, I think from Texas Instruments, called Merlin; check it out. I predicted this device on the mid-watch on a T-2 returning from Nikiske, before the pipeline, to the 2nd Mate, who was the best man with a sextant I ever saw, and who was inordinately, and justifiably proud of his skill. I was a 22 year old AB. He said," I always thought you were full of s... kid, but now I'm sure of it. That's the stupidist thing I ever heard of, a little black box you plug your sight in, and it spits out an LOP." Oh well. There are a million tricks to finding your way around the oceans off soundings. We should be exchanging what we've learned over the years. If the windjammer sailors had had the use of self-tailing winches, do you think they would have refused to use them? Of course not. But they still had the skill to haul in a line by hand without them. Every sailor should at least have a sextant aboard along with a book that can instruct them in it's use, in my opinion. I believe that GPS is God's gift to mankind by way of apology for all the grief He has caused us over the years. Cue Voice of God--" At least you idiots will always know where you are, for what it's worth".... As one of your responders says: All who wander are not lost. Fair winds, JLS