| Author |
Message |
Richard Owlett
Guest
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 Posted:
Fri Nov 18, 2005 1:08 am Post subject:
Re: Wanted: Quality Sextant |
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Dennis Pogson wrote:
| Quote: | Peter McLelland wrote:
[snip]
The main problem with the GPS is the power supply which means that the
available space for water gets taken up with batteries.
Peter
Are batteries hard to come by where you live? We seem to have a
preponderance of them.
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If you are actually concerned with "lifeboat" issues
Why not have _NO BATTERIES_ and a hand cranked generator? |
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News f2s
Guest
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| Posted:
Fri Nov 18, 2005 1:08 am Post subject:
Re: Wanted: Quality Sextant |
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| Quote: | Does anybody remember loran?
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Yup. New fangled gadget that worked with some cathode tube that
drained the batteries in two hours flat (OK, both gennies had
conked out and we had lights on down below as well). And that was
on a Corvette Needed a trained operator and some special maps.
The RDF was better - gave a bearing within 10 degrees or so.
Couple of beacons might put you within 10 miles of your position
(60% probablility) in some areas of the sea. Better than trying to
use a sextant at night. Or in cloud. Which was about 70 to 80% of
the time in northern latitudes in winter - or sometimes for days
in a row.
Ded reckoning was always more reliable than either of the last two
if you'd been less than 24 hours without a position line of some
sort. I suppose if the sun did pop out, that was one position line
to turn the circle of uncertainty into a smaller elipse.
Then radar came along. Flattened the batteries even quicker, and
needed a special interpreter to operate the damn thing. But great
for seeing you were going to bump unexpectedly into a lump of
rock. Or iceberg. Couldn't tell which unless you'd been keeping a
DR plot. So we developed techniques for closing onto the land,
checking radar range for a position line, then scooting off out to
sea again.
And radar was designed to see other boats! Trouble was, other
boats learned to see your radar transmissions, then they'd pop
under the surface and poop nasties at you. All these electronic
gadgets seem to have snags.
Except GPS. Gets me back to the house every day now my memory is
going. And no-one fires torpedoes at it. Great.
I think the original poster got the right idea. The best use of
sextants is to use them to prove to the kids the earth is round,
and spins. And it goes round the sun. I've just got round to
accepting these ideas now that I know how GPS works. And to think
I used to believe that some great guy up in the sky produced all
those tables for us so we could work out where we were on that
flat earth!
JimB |
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otnmbrd
Guest
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| Posted:
Fri Nov 18, 2005 1:08 am Post subject:
Re: Wanted: Quality Sextant |
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"News f2s" <jimb@seesignature.f2s.com> wrote in message
news:dlj1go$hr1$1@news.freedom2surf.net...
| Quote: |
Does anybody remember loran?
Yup. New fangled gadget that worked with some cathode tube that drained
the batteries in two hours flat (OK, both gennies had conked out and we
had lights on down below as well). And that was on a Corvette Needed a
trained operator and some special maps.
|
Sounds like you're talking about Loran A, not "C"..... two different
animals.
In any case, Loran is not dead ....... yet.
| Quote: |
Then radar came along. Flattened the batteries even quicker, and needed a
special interpreter to operate the damn thing. But great for seeing you
were going to bump unexpectedly into a lump of rock. Or iceberg. Couldn't
tell which unless you'd been keeping a DR plot. So we developed techniques
for closing onto the land, checking radar range for a position line, then
scooting off out to sea again.
|
LOL sounds like you're talking about the old WW2 sets
| Quote: |
I think the original poster got the right idea. The best use of sextants
is to use them to prove to the kids the earth is round, and spins. And it
goes round the sun. I've just got round to accepting these ideas now that
I know how GPS works. And to think I used to believe that some great guy
up in the sky produced all those tables for us so we could work out where
we were on that flat earth!
JimB
|
For those making long trans- ocean passages, the ability to use a sextant is
still good insurance.
otn |
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Jonathan Ganz
Guest
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| Posted:
Fri Nov 18, 2005 1:08 am Post subject:
Re: Wanted: Quality Sextant |
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In article <531ff.524904$tl2.120648@pd7tw3no>,
Gary <plumperNOSPAM@shaw.ca> wrote:
| Quote: | The GPS is just as reliable as a sextant and less fragile. Bring two if
you want redundancy. Leave the sextant back with the books and the deck
watch on your sinking ship. Grab the EPIRB and SART as you leave.
|
On my last offshore, we had five handheld GPSs and the boat GPS. The
boat GPS and one handheld were the only ones working at the end of 10
days. But, I agree with you. Just didn't bring enough batteries.
--
"j" ganz @@
www.sailnow.com |
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John
Guest
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| Posted:
Fri Nov 18, 2005 1:08 am Post subject:
Re: Wanted: Quality Sextant |
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To everyone suggesting GPS's,
He didn't ask for an alternative to a sextant. Please re-read the
original post. It's very nice that most people would choose a GPS or
EPIRB. Too bad it has nothing to do with the original post.
John |
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Phil Wheeler
Guest
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| Posted:
Fri Nov 18, 2005 1:08 am Post subject:
Re: Wanted: Quality Sextant |
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John wrote:
| Quote: | To everyone suggesting GPS's,
He didn't ask for an alternative to a sextant.
|
Maybe an Astrolabe?
He might be safer with a GPS if he travels in Kansas. We know that GPS
is OK so far (Garmin is there). But a SEXtant could get him in real
trouble :)
Of course -- not much boating in KS last I heard.
Phil |
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Jonathan Ganz
Guest
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| Posted:
Fri Nov 18, 2005 1:08 am Post subject:
Re: Wanted: Quality Sextant |
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In article <yc5ff.7324$QM5.3640@tornado.socal.rr.com>,
Phil Wheeler <w6tuh-ng4@yahoo.com> wrote:
| Quote: | John wrote:
To everyone suggesting GPS's,
He didn't ask for an alternative to a sextant.
Maybe an Astrolabe?
He might be safer with a GPS if he travels in Kansas. We know that GPS
is OK so far (Garmin is there). But a SEXtant could get him in real
trouble :)
Of course -- not much boating in KS last I heard.
|
Waves of grain.
--
"j" ganz @@
www.sailnow.com |
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Vic Fraenckel
Guest
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| Posted:
Fri Nov 18, 2005 8:47 am Post subject:
Re: Wanted: Quality Sextant |
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Gordon,
You wrote:
| Quote: | A simple solar powered calculator now costs less than $10. An angular
measuring device (precision potentiometer), a few bucks.
Why not marry it altogether to create a sextant that automatically
figures lat and long as soon as you push a button telling it you just shot
the sun, or moon, or Polaris.
If it stored the readings, it could even average out over time for more
accuracy.
Is this farfetched?
|
Easily within the realm of possibility!
I have often thought that it would be possible to build a all digital sextant. There are absolute angle resolvers that have the requisite accuracy and the computing power necessary to do the sight reduction is easily come by in a small enough package. I think there is no market for such a critter any more. Might be fun to have one though. This has been in my mind for many years.
Vic
--
________________________________________________________
Victor Fraenckel - The Windman
victorf ATSIGN windreader DOTcom
KC2GUI |
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Dale DePriest
Guest
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| Posted:
Fri Nov 18, 2005 9:08 am Post subject:
Re: Wanted: Quality Sextant |
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Gary wrote:
| Quote: | John wrote:
To everyone suggesting GPS's,
He didn't ask for an alternative to a sextant. Please re-read the
original post. It's very nice that most people would choose a GPS or
EPIRB. Too bad it has nothing to do with the original post.
John
The conversation has evolved. Stay with the tour.
|
Actually the amazing thing is it drifted back to on topic for this news
group.
Dale
--
_ _ Dale DePriest
/`) _ // http://users.cwnet.com/dalede
o/_/ (_(_X_(` For GPS and GPS/PDAs |
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Peter McLelland
Guest
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| Posted:
Fri Nov 18, 2005 9:08 am Post subject:
Re: Wanted: Quality Sextant |
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"Richard Owlett" <rowlett@atlascomm.net> wrote in message
news:11npqct7iect85c@corp.supernews.com...
| Quote: | Dennis Pogson wrote:
Peter McLelland wrote:
[snip]
The main problem with the GPS is the power supply which means that the
available space for water gets taken up with batteries.
Peter
Are batteries hard to come by where you live? We seem to have a
preponderance of them.
If you are actually concerned with "lifeboat" issues
Why not have _NO BATTERIES_ and a hand cranked generator?
Cranker needs more water, at the end of the day every thing in a life raft |
comes back to water.
By far the best thing of all is to have a 406 EPIRB, properly registered and
the SAR people will get to you before having GPS or a sextant or enough
water become really important.
Peter |
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News f2s
Guest
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| Posted:
Fri Nov 18, 2005 3:49 pm Post subject:
Re: Wanted: Quality Sextant |
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"otnmbrd" <otnmbrd@earthlink.net> wrote in message
news:RA8ff.1874$jI5.1667@newsread1.news.pas.earthlink.net...
| Quote: |
Sounds like you're talking about Loran A, not "C"..... two
different animals. <snips> > LOL sounds like you're
talking about the old WW2 sets
|
Exactly. Murmansk convoys. I'm not even sure it was Loran since it
was so secret it didn't have a name at the time. It was a radio
phase difference measuring system. You had to tune in, then fiddle
with oscillograph cursors to measure phase differences.
| Quote: | For those making long trans- ocean passages, the ability to use
a sextant is still good insurance.
|
Certainly feasible, especially in trade wind latitudes. And fun,
if you're getting bored. And good for one's self esteem -
exercising an archaic skill. I guess you'd not agree with my use
of the word 'archaic' here.
Insurance? Yes, I'd go along with that. 'Good' insurance? That
implies value for money - or value for effort in this case. That's
maybe where we differ. The effort of sextant position lines is
high compared to having a second GPS aboard - spare batteries and
all. And GPS hasn't gone off air yet for more than one day in its
many years of operation, so its not going to go missing during my
next voyage.
JimB |
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Gary
Guest
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| Posted:
Fri Nov 18, 2005 5:08 pm Post subject:
Re: Wanted: Quality Sextant |
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Tapio Sokura wrote:
| Quote: | Gary wrote:
Meanwhile, you could buld one:
http://www.tecepe.com.br/nav/CDSextantProject.htm
I built one of those last summer. With four shots of the moon using an
artificial horizon I got to within 5 nm of my actual position. The LOPs
all met at roughly the same place on a plotting sheet and the "error
polygon" was in diameter a lot smaller than the actual error. So I might
have made some systematic errors while doing the calculations, should
redo the stuff some day..
Tapio
Very nice. Did you make the artificial horizon too? I understand that |
you can use a pan of cooking oil and divide the observed angle between
the body and it's reflection in half for a makeshift artificial horizon.
A 5 mile error is certainly acceptable on a field expedient sextant.
Gaz |
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Tapio Sokura
Guest
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| Posted:
Fri Nov 18, 2005 5:08 pm Post subject:
Re: Wanted: Quality Sextant |
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Gary wrote:
I built one of those last summer. With four shots of the moon using an
artificial horizon I got to within 5 nm of my actual position. The LOPs
all met at roughly the same place on a plotting sheet and the "error
polygon" was in diameter a lot smaller than the actual error. So I might
have made some systematic errors while doing the calculations, should
redo the stuff some day..
Tapio |
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Armond Perretta
Guest
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| Posted:
Fri Nov 18, 2005 5:08 pm Post subject:
Re: Wanted: Quality Sextant |
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[trimmed to r.b.c]
Gordon wrote:
| Quote: | Regarding sextants: An idea!
A simple solar powered calculator now costs less than $10. An
angular measuring device (precision potentiometer), a few bucks.
Why not marry it altogether to create a sextant that automatically
figures lat and long as soon as you push a button telling it you just
shot the sun, or moon, or Polaris.
If it stored the readings, it could even average out over time for
more accuracy.
Is this farfetched? ..
|
Yes. A single reading, or an averaged set of readings on the same body,
does not "automatically figure lat and long." A single reading yields a
line of position.
In any case you are late to the table since attachments like this were
available at least 15 years ago.
--
Good luck and good sailing.
s/v Kerry Deare of Barnegat
http://home.comcast.net/~kerrydeare |
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otnmbrd
Guest
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| Posted:
Fri Nov 18, 2005 5:08 pm Post subject:
Re: Wanted: Quality Sextant |
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"News f2s" <jimb@seesignature.f2s.com> wrote in message
news:dlk872$rfi$1@news.freedom2surf.net...
<snip>
| Quote: |
Insurance? Yes, I'd go along with that. 'Good' insurance? That implies
value for money - or value for effort in this case. That's maybe where we
differ. The effort of sextant position lines is high compared to having a
second GPS aboard - spare batteries and all. And GPS hasn't gone off air
yet for more than one day in its many years of operation, so its not going
to go missing during my next voyage.
JimB
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<G> Dating myself, but I've used both Loran A and those old style radars
(limited use on the radar).
At any rate, as to your last paragraph ...... I consider it less a question
of effort and more a question
of preparing for "worst case" scenarios.
In the end, the importance any one individual will place on what equipment
they carry will be based on
many factors ..... for me, trans-ocean, I will have a sextant (<BG> not my
Plath) ....... may never use it, but
it will be there.
otn |
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