Sextant Newbie?

[Andrew Troup]

Originally Posted by Bash

Claiming you want to learn to use one because you don't trust electronic gadgets is like going into battle with a sword because you don't trust guns.

Hmm- if I was going into certain battle situations

(unlikely, being a rabid pacifist)

I would definitely take something(s) stealthier than a gun, like a knife, a garotting wire, a syringe....

Of course, being a determined coward, fond of staying alive, I'd take the best gun(s) available. And hope they didn't jam.

Peter Blake's gun jammed.

[goboatingnow]

Learn celestial if you like to do it , a kind of hobby , that's what I like. Currently I'm working my way through Bruce Starks method of clearing Lunars to determine time
But don't other as a backup to GPs. You simply won't use it enough and when the time comes you'll be rusty and make errors. Unless you use celestial regularly the skills set fades.

The fact is you'll spend most of your sailing life waiting for all your gps devices to fail.

Dave

[goboatingnow]

Originally Posted by Andrew Troup

It never fails to amuse me when accuracy is advanced as the clincher for using a second GPS as sole backup for a GPS.

Because, quite often, the same person will (if pushed to acknowledge a certain degree of risk inseparable from having 'all eggs in one basket')

then turn around and say:

< <What's the big deal if you do get some sort of multiple failure ?:

It's not rocket science:you just sail west (or whatever) until you see land then turn right (or whatever) > >

I'm not sure why pinpoint accuracy is so essential to the first proposition,
when the second proposition flings it out the window.

There is no confusion, there is no need for precision position fixing to navigate by. GPS gives that but it is unnecessary. If or when it fails , an unlikely proposition, one can do elementary non precise navigation by a number of methods. No more then a competent navigator can reach land without a GPs, he can reach it without a sextant.

Dave

[Lagoon4us]

Claiming you want to learn to use one because you don't trust electronic gadgets is like going into battle with a sword because you don't trust guns!

Great Analogy

[Adelie]

Originally Posted by Lagoon4us

Claiming you want to learn to use one because you don't trust electronic gadgets is like going into battle with a sword because you don't trust guns!

Great Analogy

If you go into battle with guns and a sword and everyone else is just carrying guns, then you are a leg up on everybody else. And before you argue that the odds are infinitesimal that every gun could possibly you have on you jamming, remember this is an analogy about GPS not a discussion about guns.

There are situations that could lead to every GPS on a boat failing (low probability, but not that improbable, 3/100 to 1/10,000 per year depending on location). There are also situations that could render every GPS (and possibly the other systems too) useless. While these are essentially un-quantifiable events, I would guess that loss of one system will occur within the next 50yr and all of them within 200yr.

Still a good analogy except not with the moral originally offered.

[Adelie]

Originally Posted by goboatingnow

Learn celestial if you like to do it , a kind of hobby , that's what I like. Currently I'm working my way through Bruce Starks method of clearing Lunars to determine time

Have you read Letcher's method of Lunars, much simpler than the traditional method, less dependent on good sextant technique those potentially very tedious and time consuming.

Originally Posted by goboatingnow

But don't other as a backup to GPs. You simply won't use it enough and when the time comes you'll be rusty and make errors. Unless you use celestial regularly the skills set fades.

You are making assumptions about how much practice the OP is willing to put into this and how good his recollection will be. I know people that can recall conversations almost verbatim which amazes the hell out of me. I on the other hand recall how certain technical processes work weeks and months after the last time I used the process, which amazes those same people. Keep in mind that the OP's technical recall may be better than yours and give him/her the benefit of the doubt.

Originally Posted by goboatingnow

The fact is you'll spend most of your sailing life waiting for all your gps devices to fail.

I hope to wait my whole life for GPS to fail, but preparing the boat as if it would never happen is not the smart way to play the odds if you are going to be out for an extended period. The same as having a fire extinguisher, or a large capacity pump or a drogue/sea-anchor/series drogue, all there to deal with low probability events.

[rover88]

Originally Posted by Lagoon4us

Claiming you want to learn to use one because you don't trust electronic gadgets is like going into battle with a sword because you don't trust guns!

Great Analogy

A gun without bullets is an inefficient bludgeon. A GPS without power is an inefficient paperweight.

Why in 2013 does the USMC still issue the Kabar fighting knife? Not exactly a sword.... but you get the point (sorry.... there may be a lame pun there).

[jgbrown]

Originally Posted by rover88

A gun without bullets is an inefficient bludgeon. A GPS without power is an inefficient paperweight.

Why in 2013 does the USMC still issue the Kabar fighting knife? Not exactly a sword.... but you get the point (sorry.... there may be a lame pun there).

What's a sextant without sun?

[GrowleyMonster]

Originally Posted by jgbrown

What's a sextant without sun?

One that still has moon, stars, and planets.

[barnakiel]

Originally Posted by SkiprJohn

In my opinion if you think celestial navigation is easy then you must be doing it wrong!(...)

C'mon. Some things are easy for some and more difficult for others.


b.

[jgbrown]

Originally Posted by GrowleyMonster

One that still has moon, stars, and planets.

Fine, what do you call a sextant with constant cloud cover ?
Surely there must be a funny name for one when what it relies on to function is unavailable, like for gps or guns?

This could be a whole topic... what things are without what they use. An anchor without bottom is a poor fishing lure, an engine with no fuel is a ? a mast without sails is a ?

I like sextants, I am buying and learning to use one when I can, but it just struck me as extremely funny to define other tools by their use without what they require, when a sextant could have a similar issue...

[boatman61]

You mean like a blind man with paper charts... and not in Braille

[Hudson Force]

Originally Posted by GrowleyMonster

I would say NO on the plastic sextant for learning. The reason is, the inherent inaccuracy of the plastic instrument ..................

There's a huge amount of wise information in this long post by GrowleyMonster; however, some may not agree with the inherent inaccuracy of plastic. I can not speak with my own knowledge of the effects of the temperature expansion coefficients of the plastic and metal or to the results of these characteristics, but my own use of a plastic Davis sextant placed me regularly within ten miles of my actual position. Some may not consider this as a good record of accuracy, but I think it's a realistic expectation for sextant position fixes.

I think most of us use what we have. I certainly enjoy the accuracy of GPS, but I keep a thought to my running dead reckoning and I write down my known times and positions.

[GrowleyMonster]

Originally Posted by jgbrown

Fine, what do you call a sextant with constant cloud cover ?
Surely there must be a funny name for one when what it relies on to function is unavailable, like for gps or guns?

This could be a whole topic... what things are without what they use. An anchor without bottom is a poor fishing lure, an engine with no fuel is a ? a mast without sails is a ?

I like sextants, I am buying and learning to use one when I can, but it just struck me as extremely funny to define other tools by their use without what they require, when a sextant could have a similar issue...

You call it a sextant waiting for clear skies. Meanwhile, you still have your DR. They go hand in hand. Before GPS, before SatNav, before Decca and Loran C and Loran A and Omega, before RDF, there was sextant and DR. And it worked just fine. Sure, you sometimes go several days without a fix due to overcast. But with a careful DR, when you do get a fix, it is usually satisfyingly close to the DR position. Celestial navigation combined with a careful DR is the only realistic backup to electronic navigation. Its limitations are only limitations, not disqualifications. There are "issues" with every facet of sailing and every method we use to accomplish our objectives.

[jgbrown]

Originally Posted by GrowleyMonster

You call it a sextant waiting for clear skies. Meanwhile, you still have your DR. They go hand in hand. Before GPS, before SatNav, before Decca and Loran C and Loran A and Omega, before RDF, there was sextant and DR. And it worked just fine. Sure, you sometimes go several days without a fix due to overcast. But with a careful DR, when you do get a fix, it is usually satisfyingly close to the DR position. Celestial navigation combined with a careful DR is the only realistic backup to electronic navigation. Its limitations are only limitations, not disqualifications. There are "issues" with every facet of sailing and every method we use to accomplish our objectives.

Yes I agree. Though you could replace days with weeks around here in the winter ... I simply think is sad that the sextant was left out of the funny list and was poking a bit of fun instead of getting all serious, when it seemed a bit odd to only poke the technologies that are more recent.




Seriously, it seemed to imply the utter reliability of a sextant, at all times which I don't agree with, the limitations of a GPS are simply different.
Both are better than either alone. Few things are infallible. On land I'd have both a lighter, and fire steel, only needed the latter once was good to have then.