Jump to content

Acutal use of celestial navigation prior to the GPS era


Recommended Posts

It's January in Minnesota, my (current) boat is for sale.  I'm learning celestial navigation, partly as a mental challenge, and partly as a way to understand history.  I find it interesting: the math is easy but the arithmetic is hard.

Reading through some older tutorials and, especially, advice on how to use celestial navigation in practice on a yacht (as opposed to on a commercial or military vessel), it appears to me that actual practice was, well, a little sloppy.

Nominal practice, as I understand it, was to take a round of star sights in morning and evening twilight, with a round being 3 or perhaps 4 stars, weather permitting.  Faced with unfavorable weather at dusk or particular uncertainty regarding the effects of winds and currents, the careful navigator might also take a running fix or two from the sun or moon during the day. 

Some of the older tutorials seem to encourage people to take a noon sight (simpler to do but usually less accurate) and leave it at that, adding in some radio direction finding when approaching land.

It leads me to wonder whether most cruisers before the GPS era were perhaps on the whole masters of not caring where they were, rather than masters of celestial.

Link to post
Share on other sites

We have been doing observations on our trip to Cape Verde and will continue on the next leg across the pond.  
 

We will bring the sextant in our ditch kit along with portable gps etc.  

 

Am learning while others onboard are well versed.  Doing the math on iphone applications.  Best readings so far around 10-12 miles off gps locations. It has been hazy, though. 
 

For the RYA advanced certifications it’s required.  

Link to post
Share on other sites
1 hour ago, 2airishuman said:

 

Nominal practice, as I understand it, was to take a round of star sights in morning and evening twilight, with a round being 3 or perhaps 4 stars, weather permitting.  Faced with unfavorable weather at dusk or particular uncertainty regarding the effects of winds and currents, the careful navigator might also take a running fix or two from the sun or moon during the day. 

It leads me to wonder whether most cruisers before the GPS era were perhaps on the whole masters of not caring where they were, rather than masters of celestial.

I would have said that 'normal' practice was running sun fixes.  Stars were 'normal' only in unusually tricky places like the Tuamotus, and/or just before expected landfall (if the conditions were good).

We generally knew where we were +-30 miles - certainly a whole lot less accurate than with gps, but also generally good enough.  It could be much better than that on a good day, but you did not count on it - it might be somewhere in the 2 to 5 mile range but I did not count on it.

There was a different navigational mindset back then - use of a wider range of skills and more caution.

  • Like 7
Link to post
Share on other sites
2 hours ago, 2airishuman said:

It's January in Minnesota, my (current) boat is for sale.  I'm learning celestial navigation, partly as a mental challenge, and partly as a way to understand history.  I find it interesting: the math is easy but the arithmetic is hard.

Reading through some older tutorials and, especially, advice on how to use celestial navigation in practice on a yacht (as opposed to on a commercial or military vessel), it appears to me that actual practice was, well, a little sloppy.

Nominal practice, as I understand it, was to take a round of star sights in morning and evening twilight, with a round being 3 or perhaps 4 stars, weather permitting.  Faced with unfavorable weather at dusk or particular uncertainty regarding the effects of winds and currents, the careful navigator might also take a running fix or two from the sun or moon during the day. 

Some of the older tutorials seem to encourage people to take a noon sight (simpler to do but usually less accurate) and leave it at that, adding in some radio direction finding when approaching land.

It leads me to wonder whether most cruisers before the GPS era were perhaps on the whole masters of not caring where they were, rather than masters of celestial.

I used celestial frequently when I was young … no other choice 

celestial is never “ accurate “ 

on a as small craft you use the sun and generate LOPs, not fixes 

In northern waters the stars are never or rarely used 

you work the sun all day long 

with good DR skills and an a LOP you could easily get within Radio beacon range … then follow the beacon in 

You always need THE  BOOK 

I suggest John Letchers  book

John uses  HO 208 reduction tables 

these are compact tables and are included in the textbook

john is a small craft navigator and explains the best sight combinations …like Longitude at Noon , a very powerful combination . How to construct plotting sheets from normal lined logbook paper 

a cheap plastic sextant Is all you need for accurate sun shots 

 

 

 

4EF66E6B-9236-4521-85A9-9C509411CF86.jpeg

  • Like 1
Link to post
Share on other sites

I swung a sextant on the Transpac.  We had Loran C and a beta test GPS (spotty satellite coverage hindered it) but, if I recall correctly, I had to submit 3 position fixes to be scored.  I took noon sights because it was so much easier.  The ancients didn't have accurate time while I had a quartz watch synched to time from a radio station in CO.  I still remember how amazed I was at how far the sun traversed in a minute.

  • Like 2
Link to post
Share on other sites

Getting any kind of LOP from any source when you can is how I did it.  Clouds, fog, and bad horizon is the main obstacle.  So you need to be ready whenever conditions allow.  That means keeping a constant update of DR track, working twilight sights up well in advance, doing any sun or moon shots when conditions are right, having tables with blanks ready to fill in.  On a sailboat, rough conditions makes sights hard.  Find a spot where you can stabilize yourself as best you can before the time to take a sight.

Before electronic stuff, it was a full time job. 

  • Like 1
Link to post
Share on other sites
3 hours ago, 2airishuman said:

masters of not caring where they were

yea, this is perhaps a significant misunderstanding of the situation. 

Like today, like always, there were careless people and careful people.  There were surely some people who did not care so much and there were certainly lots of people who cared quite a bit.

But as @bgytr says, it was a near full time job to know where you were back then, and there were many many fundamental environmental limitations on accuracy which all the 'caring' in the world could not eliminate.  I knew how to lunars back then (which would have been rare but I was a math guy) but there was no way in hell I was ever going to pull that off on a small boat at sea and I did not need to (and tables were extremely hard to come by for it).  People did what was necessary to get where they were going as safely as possible.

 

you should give it a try - turn off your gps (dont use your gps for the assumed position, as that is cheating big time), head out to sea for a few days and see how it goes.

  • Like 4
Link to post
Share on other sites

And looking through the Pilot at the coastal profile pics to see where you actually made landfall after no sights for over 3 days.  A deep depth sounder was a useful bit of navigational kit too.

 

Link to post
Share on other sites

I've read a few logs from old sailing vessels - "the pros" - and was struck by how often they would discover that their plot was off by hundreds of miles.  (Lack of clear skies may have had something to do with it.) I guess you just keep doing it often enough that the errors get corrected by the time you get to the other side of the ocean.  OTOH, lots of not-particularly gifted people navigated their way to small islands BITD.

A couple of winters ago, I worked my way through the Starpath books (sans clear skies) but haven't tried it at sea.  The calculations are not all that fun to do without some clear application.  And I didn't particularly like the way those lessons were all about working through the mechanical process without explaining the why. But at least after you work enough problems you get the feel of why the tables are set up the way they are.  And how easy it is to make stupid little errors.  

Anyhow, the celestial stuff is in the pile of things that "would be nice to take" on the boat, if there ends up being room for them.  They might be competing with the sewing machine.  

 

  • Like 1
Link to post
Share on other sites

I have been delivering yachts since the early eighties when there was no other way. It got so I could rip off a sun sight in well under a minute from taking out my sextant to a line on the chart. A noon sight is quicker. I used "air tables" as it's the quickest easiest way. I had a very good Zeiss sextant and was very practiced. There were a couple of years I recorded around 300 days a year at sea and more than a few over 150. Nearly all of it is sun-run-noon-run-sun. Nearing a landfall or hazard I would use morning/evening stars. Polaris is spectacularly useful in the N hemisphere as it gives you a quick and accurate latitude with little arithmetic.

"Accurate" was within ten miles. And so we worked with that. Always assume the worst position you could be in and work from there. I sailed in the Tuamotu in 89 and it was stressful, but doable. Curiously the rate of boats sinking etc from not knowing their position has not decreased with the advent of GPS. Because the rate of stupidity hasn't. And I am not calling anyone out ....I have had a few very lucky escapes...

The chief source of innacuracy in historical ships positions was innacurate timekeeping. The advent of digital watches and short wave time signals meant that longitude was much more accurate. Latitude was always good as a noon sight is independent of timekeeping. That is why ships practiced latitude sailing. They knew the latitude of a small island was accurate so they got on the right latitude early and sailed along it until they found the island. It wasn't uncommon for longitude to be 30 miles out or more. On that note some charts are still derived from data from this era. If you sail in out of the way places where there is no commercial imperative to spend tens of millions resurveying with modern equipment then it's as well to check the data on which the chart is based. The GPS is always accurate, but is the chart? Much of the non-French South Pacific falls into this category.

 

  • Like 3
Link to post
Share on other sites
4 hours ago, estarzinger said:

I would have said that 'normal' practice was running sun fixes.  Stars were 'normal' only in unusually tricky places like the Tuamotus, and/or just before expected landfall (if the conditions were good).

We generally knew where we were +-30 miles - certainly a whole lot less accurate than with gps, but also generally good enough.  It could be much better than that on a good day, but you did not count on it - it might be somewhere in the 2 to 5 mile range but I did not count on it.

There was a different navigational mindset back then - use of a wider range of skills and more caution.

This was my practice as well. Mid-morning sunline, noon latitude, afternoon sunline. Realistically, if you are running a good DR, your AM/PM sunlines should confirm your DR course and longitude, and your noon sight your latitude. With accurate time, your noon latitude yields a good longitude as well, which should line up with your AM/PM sunlines.

Quartz watches in the late 70s gave accurate, reliable wrist-watch time that was previously unavailable, making celestial a precision game for anyone with the will and patience to learn.

I used a simple TI scientific calculator, although I had a couple of different hand-held dedicated celestial calculators at some point. I probably still have those in a box somewhere.

TI actually produced a worksheet for using their scientific calculator for celestial navigation. I still have a pad of those worksheets. They also produced a great little soft-cover book titled "Student Calculator Math" for use with their original TI-35 scientific calculator. (Still have that book.)

I started out with H0 229 and the Nautical Almanac. I also had (still have, sitting on a shelf) a hand-held RDF for approaches on places with RDF beacons, such as Bermuda.

When the Marion-Bermuda race started in 1977, you could only use celestial. That was my baptism by fire in ocean racing. Pleased to say I won that overall as navigator twice as in a row with two different boats back then, plus another first in class the next time.

I've had a Husun (Henry Hughes and Son) ex-Admiralty sextant since the late 1970s.  Mirrors were re-silvered and calibration checked by R. E. White Instruments in Boston many years ago. I even built a fitted rack for it under the chart table on my last boat, but it never came out of the box during a 30,000+ mile circumnavigation. Why make it hard on yourself?

 With celestial navigation, it's all about practice. That, and really good DR.

Many of us who were not professional mariners back then started out with a little green book titled "Celestial Navigation for Yachtsmen", by "Mary Blewitt." In real life, Mary Blewitt was Mary Pera, a larger than life figure in English yachting, and a well-respected expert on the Racing Rules of Sailing. I once bought her a drink at the bar at the Royal Ocean Racing Club on St. James Place in London, just to thank her for all the joy and success her little book had brought me over the years.

That was the type of thing you did back then.

  • Like 5
Link to post
Share on other sites

No one has noticed that 2air said it’s January in Minnesota, he’s there, and why? :-). Sounds like a place to escape from in winter :-)  But seriously, I imagine that there’s lots of sun on those blisteringly cold prairie winter days.  So, since there’s sun (as compared to the perennially dark-and-cloudy-in-winter rain forest coast I live on), just whip out the sextant and an artificial horizon and practice sight taking.  I should be so lucky! :-)

  • Like 1
Link to post
Share on other sites
5 hours ago, slug zitski said:

I used celestial frequently when I was young … no other choice 

celestial is never “ accurate “ 

on a as small craft you use the sun and generate LOPs, not fixes 

In northern waters the stars are never or rarely used 

you work the sun all day long 

with good DR skills and an a LOP you could easily get within Radio beacon range … then follow the beacon in 

You always need THE  BOOK 

I suggest John Letchers  book

John uses  HO 208 reduction tables 

these are compact tables and are included in the textbook

john is a small craft navigator and explains the best sight combinations …like Longitude at Noon , a very powerful combination . How to construct plotting sheets from normal lined logbook paper 

a cheap plastic sextant Is all you need for accurate sun shots 

 

 

 

4EF66E6B-9236-4521-85A9-9C509411CF86.jpeg

I recognize that book, wonder what happened to my copy? We only did sun sites. If often seemed to get cloudy when you really wanted a good site. Certainly much more skill needed back then balancing celestial, DR, RDF, place contrails, ship passing. GodI must be old.

Link to post
Share on other sites

I never had to use it. I had GPS when I went offshore. But I programmed my HP calculator to solve the navigational triangle using haversine equations found in Bowditch. Basic idea is start from an assumed position and only correct it toward or away from the body you are sighting. I did it once in the middle of the pacific and I was not far off of what the GPS said.

To me, all the form-based methods were too confusing. I couldn't really understand what I was doing. I would calculate my distance from the assumed position to the geographical position of the body observed. Then compare the corrected sextant reading to that distance. I would correct the assumed position toward or away from the body depending on the corrected sextant reading.

This pretty much works for any body any time. If you do a real multi-star fix (which I didn't do) you could draw lines on a chart for each star, then your new assumed position is the center of mass of the triangle formed.

Link to post
Share on other sites

In college I was taught to solve the navigational triangle with spherical trigonometry and a calculator and to work with decimal degrees

its easier to use the standard sight reduction forms  on a small craft 

the secret to celestial is  accurate altitude and time recordings 

professional navigators taught  me several tricks to maintain  accuracy and repeatability 

the tables and forms are simple , plotting is simple 

accurate DR is a seaman’s skill 

celestial on a small craft is not about accurate positions , its about situational awareness 

And forget about stars.. first master the sun , then master the moon , then master Venus … these are all doable sights on a small craft 

  • Like 1
Link to post
Share on other sites
10 hours ago, El Borracho said:

A vital skill with celestial is the ability to stand offshore for days or weeks waiting to enter a fog-bound port. Also creeping along on soundings. 

This is the secret .. timing landfall and patience 

i can remember several landfalls with primitive navigation having to hove to and Waite until things made sense

bermuda is the classic, the Gulf Stream is so unpredictable that all you knew was that you were 50 or so miles NE of bermuda .. you then had to stop , look for airplanes , ships , clouds …  monitor for the radio beacon then  identify the reef  

Mt Pico in the Azores was another …stay south of Horta , slow down and Waite for things to make sense with bearings  on pico 

 

 

  • Like 1
Link to post
Share on other sites

In the late 70's and early 80's we were routinely doing longish offshore passages several times a year. You used everything available. Maintained a detailed log and Dead Reckoning plot, RDF, and sun sights, and you'd wind up with a circle on a paper chart, that you felt pretty comfortable you were probably somewhere inside. Had a nice Plath sextant, used a Zenith Transoceanic shortwave receiver to pick up the time signal and set the chronometer. Bought the Tamaya NC-77 when it first came out, and that made working up positions easier, but didn't improve the accuracy (except for math errors), which depends of the sight itself. When we brought aboard a Loran C receiver I continued the same process above, then turned on the C to see how far off I was. But it's always (and still) a good idea to be a little skeptical of where your instruments and plots tell you that you are, especially when in the vicinity of hazards. Just yesterday my GPS/chartplotter showed us moving across dry land, at least 75 yards from our actual position.

image.png.da0e0a517490d04e562fddb9a861402a.png

  • Like 1
Link to post
Share on other sites

I used to give pre-race talks on navigation for new offshore sailors in pre-GPS days. I would describe offshore navigation to them as a brute-force process: use every tool in your toolbox to figure out where you are.

Younger sailors here will probably not remember loran charts with loran time difference curves plotted on them. These were basically electronic LOPs that you used for plotting exactly like the LOPs you derived from celestial navigation.

Remember one of the first "consumer" Loran-C units with the capability to calculate position rather than give you LOPs? I believe it was the Texas Instruments TI-2000, and it cost about $2000 US in 1980.

I thought I had died and gone to heaven racing on a boat with one of those for the first time around 1980.

Link to post
Share on other sites

It is actually quite surprising what you can do navigationally with limited information.

These guys (a pair of young french guys . . . of course) made a 27 day crossing from france to Guadeloupe, and made accurate landfall on Guadeloupe (the intended destination) with no navigation instruments (no compass, no watches, no charts maps or documents, obviously no radio or sextant).

The method was to sail SW very roughly by the sun direction, until they get to the latitude of Guadeloupe, which they would know because one particular constellation would be just above the horizon, and then head west running down the latitude. So, they really just needed one precision piece of information to make it (the constellation).  Ofc harder than it sounds to pull off in practice.

There have been a bunch of other 'no instrument' voyages (not to mention the polynesians), including a rtw, but I always found this one particularly interesting because of their precision landfall and simple direct technique.

--------------------------------------------

sort of funny - a bunch of us old guys going on about how hard it was when we had to walk to school in the snow in our bare feet uphill both ways :)

 

 

  • Like 2
Link to post
Share on other sites

As a teenager, I kind of caught the end of it.  I had the chance to sail with a crusty old couple who kept a surprisingly accurate DR, did 3 sights a day weather depending, were very, very, picky about watch keeping habits; very, very picky about how everything on the boat got done (do it wrong, you heard about it), were the worst cooks I ever sailed with and probably drank a bit too much.  We used a leadline to confirm the bottom composition, and RDF and hand bearing compass to run LOPs.  The engine was unreliable, so everything was done under sail. Unfortunately, I was too busy being a teenager that knew everything to really appreciate what I was being shown.  

  • Like 2
Link to post
Share on other sites

I did the '84 Newport-Bermuda race, no GPS. Our naviguessor got us there perfectly.

As we approach the finish, we hear a boat hail the RC to let them know they were withdrawing from the race as they were actually 50+ miles south of Bermuda........

How many times do you think that naviguessor rechecked his last calcs before going up on deck?

  • Like 1
Link to post
Share on other sites
41 minutes ago, Liquid said:

as they were actually 50+ miles south of Bermuda........

One time we were approaching Bermuda from the north, saw a sail on the horizon, who turned to close with us.  He knew he was somewhere close to bermuda but had been circling around for 3 days and just could not find it.  We told him to just follow us.  But apparently we were too slow because that night he charged off ahead.  We got in the next morning (had been timing it for that) and he then did not get in for another 3 days lol - apparently missed the island over night (which puzzled me because there are or were some pretty decent lights, but single hander/fatigued things happen I guess.).

  • Like 1
Link to post
Share on other sites
41 minutes ago, Liquid said:

I did the '84 Newport-Bermuda race, no GPS. Our naviguessor got us there perfectly.

As we approach the finish, we hear a boat hail the RC to let them know they were withdrawing from the race as they were actually 50+ miles south of Bermuda........

How many times do you think that naviguessor rechecked his last calcs before going up on deck?

1984 was very rough for about half the race. We seemed to go upwind in 25-35 knots of wind forever, as I recall, particularly in the Gulf Stream. The boat I raced on that year had a lot of issues--seasickness, torn sails, and an exploding holding tank being the primary ones. 

It is funny in hindsight, but was anything but funny at the time. One the plus side, I made one good friend on that trip that I have since raced with for thousands of miles.

  • Like 1
Link to post
Share on other sites
47 minutes ago, Liquid said:

I did the '84 Newport-Bermuda race, no GPS. Our naviguessor got us there perfectly.

As we approach the finish, we hear a boat hail the RC to let them know they were withdrawing from the race as they were actually 50+ miles south of Bermuda........

How many times do you think that naviguessor rechecked his last calcs before going up on deck?

1984 was pre-GPS for civilians by a number of years.

Link to post
Share on other sites
26 minutes ago, accnick said:

1984 was very rough for about half the race. We seemed to go upwind in 25-35 knots of wind forever, as I recall, particularly in the Gulf Stream. The boat I raced on that year had a lot of issues--seasickness, torn sails, and an exploding holding tank being the primary ones. 

That's the one...

I swear our navi never left the nav station for 2+ days but to take sightings, lots of sun shots. He never got seasick - the old bastard!

5 days to get there, half upwind in 25-35, in a C&C 40 with I think 11 onboard, severely clogged head, leaking diesel tank, shredded jibs, half the crew seasick... However, 4 glorious days to get home on a fair weather, single tack with only 5 onboard - ahhhhhhh.

I was only 18 but that was the first and only time I've been seasick. Wow, being seasick just fucking sucks! I remember puking over a main winch while grinding thru a tack! Also, square waves, no chance of staying dry, no food, no sleep as I had to pin myself in the bunk, pissing in the cockpit, trying to get the #3 jib down now that it's in 2, soon to be 3 pieces- at 2AM, then looking up and seeing a clear, Milky Way filled sky above!

I did hear on the docks that that race dusted so many veterans with seasickness that it was cool to admit it...

Link to post
Share on other sites

Disclaimer, I've never made an ocean passage as -the- primary navigator. But did navigate before GPS but after the advent of cheap good timepieces (Seiko crystal) and a few times had better fixes than the real nav guy.

The hard part is knowing what corrections to add and which ones to subtract, and if you're working in minutes and seconds, to get that to come out right. I'm the type of guy that triple-checks everything, and I've seen people trip up going from minutes and decimal seconds, to decimal minutes. Etc etc.

I enjoy the physical skill of getting a good sight at sea. It's trickier than the books let on. And you have to practice hacking the seconds, unless you have a helper which I never did.

Remember, the old fashioned nav work includes updating your ded reckoning which we always did 4 times a day at a minimum; this is overkill at sea but it also keeps a healthy routine. When I first did passages with family and family friends, boats didn't have depth sounders either!

- DSK

  • Like 1
Link to post
Share on other sites
32 minutes ago, Liquid said:

That's the one...

I swear our navi never left the nav station for 2+ days but to take sightings, lots of sun shots. He never got seasick - the old bastard!

5 days to get there, half upwind in 25-35, in a C&C 40 with I think 11 onboard, severely clogged head, leaking diesel tank, shredded jibs, half the crew seasick... However, 4 glorious days to get home on a fair weather, single tack with only 5 onboard - ahhhhhhh.

I was only 18 but that was the first and only time I've been seasick. Wow, being seasick just fucking sucks! I remember puking over a main winch while grinding thru a tack! Also, square waves, no chance of staying dry, no food, no sleep as I had to pin myself in the bunk, pissing in the cockpit, trying to get the #3 jib down now that it's in 2, soon to be 3 pieces- at 2AM, then looking up and seeing a clear, Milky Way filled sky above!

I did hear on the docks that that race dusted so many veterans with seasickness that it was cool to admit it...

We won our class in that race 

yacht Full Cry 

luck

the big New York yacht club guys on board all got seasick 

me and my mate were the only ones left sailing 

As the sun was setting the fleet tacked to starboard , we shout down below … DO WE TACK ? big guys were all incapacitated, projectile vomiting … no answer …so we continued on port tack all night … got almost one hundred miles to the west of rhumb  line   …. 
good luck move , sailed into a huge header , when we tacked the next day  we were lifted up to  layline 

won class and the governors trophy …boat that won its class by the largest margin 

good to be lucky 

 

 

  • Like 1
Link to post
Share on other sites
8 hours ago, slug zitski said:

This is the secret .. timing landfall and patience 

i can remember several landfalls with primitive navigation having to hove to and Waite until things made sense

bermuda is the classic, the Gulf Stream is so unpredictable that all you knew was that you were 50 or so miles NE of bermuda .. you then had to stop , look for airplanes , ships , clouds …  monitor for the radio beacon then  identify the reef  

Mt Pico in the Azores was another …stay south of Horta , slow down and Waite for things to make sense with bearings  on pico 

 

 

It was very poor planning to put the reef on the NW side of Bermuda, the direction from which most people are coming. I remember on our first (celestial nav) trip from NYC to Bermuda having three cruise ships overtake us, exactly on our course, about four days out (slowish boat). Made me feel a lot better about my naviguessing.

  • Like 1
Link to post
Share on other sites

First 5 deliveries HI to the west coast I did were all solely celestial. Like the Polynesians, you got good at looking for signs of closing the coast. Kelp, water color change, smell, smog, all got factored in. Just ran noon sights until 2 - 3 days off the coast, no need to be any more accurate than that, theirs nothing out there to worry about. If you took sights/times approaching LAN, and a few after your peak altitude, you can plot them out and verify your accuracy (or extrapolate the LAN) as the curve of the altitude is a flat topped bell curve.

    One trip HI to Seattle we made landfall (?? very, very thick fog) to the entrance of the Straits after 5 days of no clear sky, morning/noon/night. Quite uncertain of our position.  Finally heard a fog bouy off in the distance - motored over to it to identify it & fix our position. It was not on the chart, not in the coast pilot, not in the notices to mariners we had diligently written down before departing. Got on the VHF & called up the US Coast Gaurd - they could not identify it, tried telling us we weren't timing the horn signal right. So we held the mic out the hatch so they could time it. After 30 minutes or so the Canadian CG came up & said they had just replaced that bouy, the notice hadn't gone out yet. We were close to the coast of Victoria Is, not the South (US) coast we were aiming at

  • Like 2
Link to post
Share on other sites

If I recall correctly Robin Knox-Johnston states in his book that he only used sunsights on his circumnav.

'Sun -run - sun'  would be all that most people would require. Sun's azimuth  right astern or right ahead in the morning followed by a second sight when the azimuth is on the beam.  

Back that up with another sight in the afternoon when the azimuth is again right ahead or right astern. Plenty good enough on an ocean passage.

Stars easy enough to take if you have only a slight sea and a good horizon and stick to the brighter ones like Canopus and Sirius. A couple of stars in Orion are handy cos they are very easy to find. Morning stars start with the stars to the east - thats where you will first have a useable horizon, evening stars the opposite. Chuck in Venus if you can.

The workings would be a bit of a chore if doing it longhand/ logs  by haversine formula  but not too bad if you did them twice a day for a spell.

Pre working is the key and the best for stars is the Air Tables. They make pre calculating the altitudes easy. Combine them with the american plotting sheets and life is near perfect.

  • Like 1
Link to post
Share on other sites
On 1/14/2022 at 11:04 AM, 2airishuman said:

 I'm learning celestial navigation,

Something that might interest you:

GPS anti-spoof app for iPhone and Android that is great way to verify your sights as a learning tool. It has user-configurable settings for index correction, height of eye (and temp and pressure), so you could set it to display a computed sextant altitude, Hs, that you can compare to what you just shot.  Also has a “pause” button, so that if you have a second person as a time keeper, they can hit it (to freeze the time of the sight) when you say “mark”.

I read that you could also use the app in this way for practice, to generate virtual sight data without an actual sextant or horizon.

http://reednavigation.com/GPSantiSpoof/

  • Like 1
Link to post
Share on other sites

Humbug.  I already have a star-watching app sending me pop-up notifications about all the cool things visible "up there" somewhere above the cloud layer.

Here, it is just fog over ice, day after day.  "The Sun" is merely the supposed source of the dim directionless light that appears for a few hours around noon.  I keep expecting to see an army of naked dead people with glowing blue eyes shuffle out of the woods.  On days that I can actually see as far as the tree line.  

Oh, Oh! How about an app that displays images of the sun and stars on a big-screen TV, so you can practice taking sights?  Wiring up the TV on the ceiling would be an interesting break from shoveling snow and ice.  Or better yet, a bracket that clips your phone over the sextant so that images of celestial bodies appear in the correct positions!  Full-cycle futility.  

Link to post
Share on other sites
42 minutes ago, toddster said:

Humbug.  I already have a star-watching app sending me pop-up notifications about all the cool things visible "up there" somewhere above the cloud layer.

Here, it is just fog over ice, day after day.  "The Sun" is merely the supposed source of the dim directionless light that appears for a few hours around noon.  I keep expecting to see an army of naked dead people with glowing blue eyes shuffle out of the woods.  On days that I can actually see as far as the tree line.  

Oh, Oh! How about an app that displays images of the sun and stars on a big-screen TV, so you can practice taking sights?  Wiring up the TV on the ceiling would be an interesting break from shoveling snow and ice.  Or better yet, a bracket that clips your phone over the sextant so that images of celestial bodies appear in the correct positions!  Full-cycle futility.  

Dude, you gotta move to a sunnier place :-)

Link to post
Share on other sites
5 hours ago, Cisco said:

If I recall correctly Robin Knox-Johnston states in his book that he only used sunsights on his circumnav.

'Sun -run - sun'  would be all that most people would require. Sun's azimuth  right astern or right ahead in the morning followed by a second sight when the azimuth is on the beam.  

Back that up with another sight in the afternoon when the azimuth is again right ahead or right astern. Plenty good enough on an ocean passage.

Stars easy enough to take if you have only a slight sea and a good horizon and stick to the brighter ones like Canopus and Sirius. A couple of stars in Orion are handy cos they are very easy to find. Morning stars start with the stars to the east - thats where you will first have a useable horizon, evening stars the opposite. Chuck in Venus if you can.

The workings would be a bit of a chore if doing it longhand/ logs  by haversine formula  but not too bad if you did them twice a day for a spell.

Pre working is the key and the best for stars is the Air Tables. They make pre calculating the altitudes easy. Combine them with the american plotting sheets and life is near perfect.

Why would you not take a noon sight, and kill two birds with one stone? With an accurate timepiece, you get latitude by declination and longitude by GHA with the noon sight.

  • Like 1
Link to post
Share on other sites
3 minutes ago, accnick said:

Why would you not take a noon sight, and kill two birds with one stone? With an accurate timepiece, you get latitude by declination and longitude by GHA with the noon sight.

A noon sight can be time consuming , during this extended period a  cloud could ruin your sight 

longitude at noon is indeed a good practice 

multiple sun shots.., LOPs morning and afternoon , whenever you can see the sun and horizon ,are the goal

Link to post
Share on other sites
4 hours ago, slug zitski said:

A noon sight can be time consuming , during this extended period a  cloud could ruin your sight 

longitude at noon is indeed a good practice 

multiple sun shots.., LOPs morning and afternoon , whenever you can see the sun and horizon ,are the goal

If you keep a decent DR, you will know within a few minutes of when to start looking for LAN, so it's not like you're taking noon sights for a half hour to try to catch the sun at its maximum elevation.

I agree, take mid-morning and mid-afternoon sunlines as well.

This assumes, of course, that sea and sky conditions make that practical.

 

Link to post
Share on other sites

If you've taken enuff before/after LAN shots to plot a good curve, you can extrapolate actual LAN from your graph. Not perfect, but will give a position better than DR

  • Like 1
Link to post
Share on other sites
2 hours ago, slug zitski said:

Hard to find a nautical almanac…hard to find tide tables in a marine store 

everything is electronic these days 

 

Here you go, https://thenauticalalmanac.com/TNARegular/2022_Nautical_Almanac.pdf

What I have done in the past is download the PDF and then print out the daily pages that cover any passage I am making.

 

Beats paying $A90 for something you may only use for a few weeks

https://www.boatbooks-aust.com.au/product/np314-22-the-nautical-almanac-2020/

  • Like 1
Link to post
Share on other sites
16 hours ago, accnick said:

Why would you not take a noon sight, and kill two birds with one stone? With an accurate timepiece, you get latitude by declination and longitude by GHA with the noon sight.

Why not indeed. Often - on many 'cruiser's passages' - the sun is going to be almost on the beam at MerPass anyway.

A trap for many new players looking to use the time of merpass to establish longitude is the 'equation of time'. Ignore that or worse still apply it the wrong way and your long could be as much as 7º adrift.

 

The beauty of sights when sun is right ahead or astern and on the beam is that the latter will give a very good idea of deviation from track - left or right. The former will give a very good idea of progress along your track.

 

Link to post
Share on other sites

When standing in the wheelhouse of a ship , with Near 360 degrees of unobstructed visibility and a superior view of the horizon everything is possible 

at near sea level , in a seaway,  while flying sails  your sight choices are much reduced 

Link to post
Share on other sites
1 hour ago, slug zitski said:

When standing in the wheelhouse of a ship , with Near 360 degrees of unobstructed visibility and a superior view of the horizon everything is possible 

at near sea level , in a seaway,  while flying sails  your sight choices are much reduced 

That's odd, I have not been on very many ships but all of them had roofs over the wheelhouse and stacks and/or other superstructure blocking the view.

Going out on the bridge wing, better.

- DSK

  • Like 1
Link to post
Share on other sites
3 hours ago, Cisco said:

Why not indeed. Often - on many 'cruiser's passages' - the sun is going to be almost on the beam at MerPass anyway.

A trap for many new players looking to use the time of merpass to establish longitude is the 'equation of time'. Ignore that or worse still apply it the wrong way and your long could be as much as 7º adrift.

 

The beauty of sights when sun is right ahead or astern and on the beam is that the latter will give a very good idea of deviation from track - left or right. The former will give a very good idea of progress along your track.

 

For example, when you are sailing S from New England to Bermuda or the Caribbean, which are the routes I used to develop my celestial skills many years ago.

Link to post
Share on other sites

Are there even RDF broadcast beacons still in existence? I haven't seen an RDF receiver on a boat since the late 70s.

I thought they went the way of the dodo about the same time the various Lorans went away.

Link to post
Share on other sites
6 minutes ago, Willin' said:

Are there even RDF broadcast beacons still in existence? I haven't seen an RDF receiver on a boat since the late 70s.

I thought they went the way of the dodo about the same time the various Lorans went away.

You can also use AM radio stations and a portable radio with an internal ferrite antennae

 

accurate enough 

  • Like 1
Link to post
Share on other sites
2 hours ago, Willin' said:

Are there even RDF broadcast beacons still in existence? I haven't seen an RDF receiver on a boat since the late 70s.

I thought they went the way of the dodo about the same time the various Lorans went away.

The basic technology is still used in other fields, but there are not that many marine radio beacons left today, as far as I can tell. As Sluggo says, you can DF on an AM radio station with a directional antenna on a hand-held AM radio receiver.

I actually did that a number of years ago, in somewhat desperate circumstances.

Link to post
Share on other sites
4 hours ago, accnick said:

The basic technology is still used in other fields, but there are not that many marine radio beacons left today, as far as I can tell. As Sluggo says, you can DF on an AM radio station with a directional antenna on a hand-held AM radio receiver.

I actually did that a number of years ago, in somewhat desperate circumstances.

I’ll bet it’s a great story - let’s hear it!  (If you don’t mind.)

Link to post
Share on other sites
9 hours ago, accnick said:

The basic technology is still used in other fields, but there are not that many marine radio beacons left today, as far as I can tell. As Sluggo says, you can DF on an AM radio station with a directional antenna on a hand-held AM radio receiver.

I actually did that a number of years ago, in somewhat desperate circumstances.

https://survivaltricks.wordpress.com/2017/01/17/navigating-with-an-am-mw-radio-receiver/

671A9469-DD44-4BF1-AD19-9D89EEF190EC.png

Link to post
Share on other sites

The same radio that you use to listen for “ Iron Mike “ high seas weather NOVEMBER MIKE NOVEMBER , NOVEMBER MIKE GOLF … has a good internal ferrite antenna that works well as a direction finder 

 

EA8F28F4-B6DF-48C7-98AD-893E96CE07D7.jpeg

B7618010-1850-41AC-9A95-33BD331465DA.png

Link to post
Share on other sites
1 hour ago, slug zitski said:

The same radio that you use to listen for “ Iron Mike “ high seas weather NOVEMBER MIKE NOVEMBER , NOVEMBER MIKE GOLF … has a good internal ferrite antenna that works well as a direction finder 

 

EA8F28F4-B6DF-48C7-98AD-893E96CE07D7.jpeg

B7618010-1850-41AC-9A95-33BD331465DA.png

Yes. It is far better to rotate for the null point (vs. the loudest). At the null point one end of the rod antenna will be pointed at the station. The rod is normally along the top edge of the receiver. Hopefully one knows which of the two rod ends points at the station as I don’t recall any easy way to disambiguate that. 

Link to post
Share on other sites
On 1/14/2022 at 8:45 PM, estarzinger said:

We generally knew where we were +-30 miles - certainly a whole lot less accurate than with gps, but also generally good enough.  It could be much better than that on a good day, but you did not count on it - it might be somewhere in the 2 to 5 mile range but I did not count on it.

There was a different navigational mindset back then - use of a wider range of skills and more caution.

It was definitely a different mindset, I've never done Celestial navigation but I have sailed in the Western English channel before "Satnav" and Decca was affordable for small boats and it was all about knowing that you weren't where you shouldn't be. So it was a mix of Dead reckoning , RF beacons, depth sounder and compass when we were surprised by fog (quite common!!!). It is a very different mindset but as long as you accept that there are places where you can't come in without visibility not as tricky as people not used to it would think.

Link to post
Share on other sites
7 hours ago, Jud - s/v Sputnik said:

I’ll bet it’s a great story - let’s hear it!  (If you don’t mind.)

This was more than 40 years ago, on a badly leaking wooden boat on the way to Bermuda.

Short version is that I was not the official navigator for the trip, but the navigator (who had never been offshore) was down with seasickness  for the whole trip, so I stepped up. I had my sextant and a first-generation digital quartz watch, a simple pocket calculator, HO 229, and an almanac. But there was a heavy overcast for days, and heavy weather to go with it. We were down to a storm jib alone for 24 hours. No possibility of a sight, and the DR was about as rough as you could get.

Instruments on board consisted of an uncalibrated Kenyon wand knotmeter--you'll need to be old to remember that one--and a good compass.

We got a position from a ship after about three days. It was startling to see a small ship making pretty heavy going of it a few miles away in those conditions, but also a relief that we knew where we were at that point in time. We were running only on a compass course after that.

After almost five days with no celestial observations, and no other boats in sight, I was seriously nervous. It was my first approach to Bermuda, ever, and only my second real offshore trip.

We had a small handheld receiver with a highly directional antenna. (Speaking of directional antennas, how many people remember rabbit ears antennas on early TV sets?) I knew the basic principle of RDF, and knew we should be within radio range of BDA based on the DR. Scanned the bands, and found a local AM station. We were far enough out that all I wanted to do was not sail past the island, so all I cared about was that the station was on Bermuda. Rotating the radio, I found a null the was pretty close to dead ahead, and took that (rightly or wrongly) as the direction to sail.

The signal was much stronger next morning, and I got a break in the clouds fairly early in the morning. Got a sunsight, but using only forms, it took me about an hour to work it out. Combining that LOP with the radio bearing and the DR told me that the island should be ahead of us, and maybe 30 miles.

The weather closed back in, so we were still sailing blind, but I told the guy on deck the island should be dead ahead of us, and that we should see it within a few hours. I was not nearly as confident as I tried to sound.

Around noon, the clouds broke and the sun came out, and there was a pink smudge on the horizon in front of us just off the starboard bow. If you're old enough, you'll remember the multi-story pink hotel (it was a Holiday Inn back then, I think) on the hill outside St. George's.

We still had to work our way around the reefs to get in, and sail through the channel to get to Hamilton, which was an all-day task. We also didn't have a working engine, so we had no juice for the VHF. The navigator had also neglected to bring detail charts of Hamilton Harbor and Great Sound.

It was luck more than skill that got us there in one piece, but it impressed on me that you needed all the available tools in the arsenal when it comes to offshore navigation, just in case things go wrong.

Bought a proper hand-held RDF (a Lokata, which I still have) after that trip, and used it delivering another boat to Bermuda a few months later, using the radio beacon on Gibbs Hill instead of a local radio station. I was also a lot more confident in my celestial by then. By the next year or so, most boats had Loran C, but I still used the RDF from time to time sailing to Bermuda. 

I have made that trip more than 30 times now, and GPS has taken much of the anxiety out of the navigation part of it. But that first trip still sticks in my mind.

 

 

 

  • Like 6
Link to post
Share on other sites
On 1/14/2022 at 2:45 PM, estarzinger said:

We generally knew where we were +-30 miles - certainly a whole lot less accurate than with gps, but also generally good enough.  It could be much better than that on a good day, but you did not count on it - it might be somewhere in the 2 to 5 mile range but I did not count on it.

There was a different navigational mindset back then - use of a wider range of skills and more caution.

 

1 hour ago, Panoramix said:

It was definitely a different mindset, I've never done Celestial navigation but I have sailed in the Western English channel before "Satnav" and Decca was affordable for small boats and it was all about knowing that you weren't where you shouldn't be. So it was a mix of Dead reckoning , RF beacons, depth sounder and compass when we were surprised by fog (quite common!!!). It is a very different mindset but as long as you accept that there are places where you can't come in without visibility not as tricky as people not used to it would think.

I'll threepeat the "good enough" different navigational mindset.

I was 13 in 1975 and crewed on an old woodie Alden 36 cutter from Halifax to Southampton (but diverted to Cardiff after bobbing around out there for 42 days).  Captain Bligh wouldn't let anyone else do anything except pump the bilge and open rusty cans of food, I was fascinated watching his celestial skills and trying to pick up anything I could.  Acutal location was always a grey area, I recall spending an agonizing 50ish miles waiting for land to finally appear where is was already supposed to be...

Cheers!

 

Link to post
Share on other sites
16 hours ago, slug zitski said:

You can also use AM radio stations and a portable radio with an internal ferrite antennae

 

accurate enough 

I was always curious about that method.

Don't you need to know how the antenna is oriented inside the radio so that you can visualize the uh...line of bearing? The ferrite antenna is just a bar with wire wrapped around it IIRC, but you kind of need to know which way it's pointed.

Link to post
Share on other sites
30 minutes ago, Ajax said:

I was always curious about that method.

Don't you need to know how the antenna is oriented inside the radio so that you can visualize the uh...line of bearing? The ferrite antenna is just a bar with wire wrapped around it IIRC, but you kind of need to know which way it's pointed.

Its usually pointed longeeways within the radio ( that's technical speak)

still plenty of non directional aero beacons out there but they are below the AM broadcast band.

Link to post
Share on other sites

I just checked on my Tecsun 680, both it and the 880 - possibly other Tecsuns as well - have Long Wave that covers the aerobeacons.

Pretty handy if you are approaching an isolated island such as Easter Island. https://wiki2.org/en/Mataveri_International_Airport

Info on frequencies is out there but not that easy to find.

 

https://www.radioenthusiast.co.uk/articles/ndb-list-1-2020/

Link to post
Share on other sites
2 hours ago, accnick said:

Instruments on board consisted of an uncalibrated Kenyon wand knotmeter--you'll need to be old to remember that one--and a good compass.

It was luck more than skill that got us there in one piece, but it impressed on me that you needed all the available tools in the arsenal when it comes to offshore navigation, just in case things go wrong.

Fun times back in the day.  Never heard it called a wand knotmeter before - is that the graduated tube with a cork inside?  They were all the rage for sailors who couldn't afford (or were too cheap) for an electronic or mechanical log!  I brought my parent's tube along as backup for the Walker taffrail log onboard the Atlantic crossing.

Cheers!

Link to post
Share on other sites
4 hours ago, El Borracho said:

Yes. It is far better to rotate for the null point (vs. the loudest). At the null point one end of the rod antenna will be pointed at the station. The rod is normally along the top edge of the receiver. Hopefully one knows which of the two rod ends points at the station as I don’t recall any easy way to disambiguate that. 

With the ferrite  rod You could be on the wrong side , but most times everything makes sense 

practice ashore to get familiar with everything 

Any  AM station will work , radio beacons are better  because of their intensity 

Link to post
Share on other sites
1 hour ago, Cisco said:

Its usually pointed longeeways within the radio ( that's technical speak)

still plenty of non directional aero beacons out there but they are below the AM broadcast band.

So in the case of my boat's stereo, it is a rectangular box and the antenna will be aligned with the long dimension of the box. When seeking the AM "beacon" am I seeking to align the ends of the antenna with the signal or the sides of the antenna?  I'm actually googling this but I know I'm not phrasing the search criteria well enough.

Basically, my boat's stereo is installed in the cabinet so that the long axis of the box is aligned fore/aft. I'm trying to determine if I would steer directly towards a signal or if the signal would be to 90 degrees of fore/aft.

Link to post
Share on other sites
1 hour ago, CriticalPath said:

Fun times back in the day.  Never heard it called a wand knotmeter before - is that the graduated tube with a cork inside?  They were all the rage for sailors who couldn't afford (or were too cheap) for an electronic or mechanical log!  I brought my parent's tube along as backup for the Walker taffrail log onboard the Atlantic crossing.

Cheers!

It was a mechanical wand that pivoted as a function of the velocity of the water going past it. It had a mechanical linkage that drove a needle on a dial. It h ad a bulkhead-mounted dial on the aft face of the deckhouse.

 As I recall, it stuck beyond the hull about 5".

Think of it as similar to a tiny version of the height wand on a foiling Moth.

  • Like 1
Link to post
Share on other sites
1 hour ago, Ajax said:

So in the case of my boat's stereo, it is a rectangular box and the antenna will be aligned with the long dimension of the box. When seeking the AM "beacon" am I seeking to align the ends of the antenna with the signal or the sides of the antenna?  I'm actually googling this but I know I'm not phrasing the search criteria well enough.

Basically, my boat's stereo is installed in the cabinet so that the long axis of the box is aligned fore/aft. I'm trying to determine if I would steer directly towards a signal or if the signal would be to 90 degrees of fore/aft.

Your boat stereo probably doesn't have an internal ferrite antenna. They are usually only found in portable radios.

Link to post
Share on other sites
On 1/14/2022 at 2:04 PM, 2airishuman said:

It's January in Minnesota, my (current) boat is for sale.  I'm learning celestial navigation, partly as a mental challenge, and partly as a way to understand history.  I find it interesting: the math is easy but the arithmetic is hard.

Reading through some older tutorials and, especially, advice on how to use celestial navigation in practice on a yacht (as opposed to on a commercial or military vessel), it appears to me that actual practice was, well, a little sloppy.

Nominal practice, as I understand it, was to take a round of star sights in morning and evening twilight, with a round being 3 or perhaps 4 stars, weather permitting.  Faced with unfavorable weather at dusk or particular uncertainty regarding the effects of winds and currents, the careful navigator might also take a running fix or two from the sun or moon during the day. 

Some of the older tutorials seem to encourage people to take a noon sight (simpler to do but usually less accurate) and leave it at that, adding in some radio direction finding when approaching land.

It leads me to wonder whether most cruisers before the GPS era were perhaps on the whole masters of not caring where they were, rather than masters of celestial.

Celestial is a *huge* pain in the ass in any kind of weather on a small boat. First off the sight from a pitching deck is liable to be inaccurate and best and then you get to sit at the pitching-yawing chart table and do math problems. This is all assuming you have clear skies and a horizon. I was happy to have a couple good sun sights in a day, that and DR would get me in RDF range.

Link to post
Share on other sites
1 hour ago, accnick said:

It was a mechanical wand that pivoted as a function of the velocity of the water going past it. It had a mechanical linkage that drove a needle on a dial. It h ad a bulkhead-mounted dial on the aft face of the deckhouse.

 As I recall, it stuck beyond the hull about 5".

Think of it as similar to a tiny version of the height wand on a foiling Moth.

Cool, never seen one, neat principle.

We had an L-shaped cylinder, graduated to identify speed in knots.  To get a boat speed reading you held it vertically over the side of the boat so that the elbow and short arm of the L were below water level facing forward, and a cork inside floated upwards based on the pressure of water flowing into the tube.  Pretty basic stuff but I remember there were lots of them around in the early 70s...

Cheers!

Link to post
Share on other sites
16 minutes ago, CriticalPath said:

Cool, never seen one, neat principle.

We had an L-shaped cylinder, graduated to identify speed in knots.  To get a boat speed reading you held it vertically over the side of the boat so that the elbow and short arm of the L were below water level facing forward, and a cork inside floated upwards based on the pressure of water flowing into the tube.  Pretty basic stuff but I remember there were lots of them around in the early 70s...

Cheers!

Pretty much the same principle that modern pitot tube knotmeters work with.

I remember seeing ads for the old-fashioned handheld devices just a few years ago, but they seem to have vanished from the marketplace now. No surprise when you can get accurate GPS speed from your phone.

  • Like 1
Link to post
Share on other sites
2 hours ago, Ajax said:

So in the case of my boat's stereo, it is a rectangular box and the antenna will be aligned with the long dimension of the box. When seeking the AM "beacon" am I seeking to align the ends of the antenna with the signal or the sides of the antenna?  I'm actually googling this but I know I'm not phrasing the search criteria well enough.

Basically, my boat's stereo is installed in the cabinet so that the long axis of the box is aligned fore/aft. I'm trying to determine if I would steer directly towards a signal or if the signal would be to 90 degrees of fore/aft.

Not all radios have directional antennas. The directional antennas ares a ferrite rods wrapped in wire:

AM MF Aerial Ferrite Bar Rod Antenna DIY AM Radio KIT ...image.png.408878360a680c4cef6077c8ffb93d88.png

 

The null off the ends is quite sharp, just a few degrees ideally. The signal peak broadside to the antenna is very large, like 45 degrees, and is not used. Resolving the 180 degree ambiguity is a bit tricky. Some of these units have a second antenna to aid with that, but I never found it to be that accurate and usually you know where the beacon should be.

Airplanes have automatic direction finders that resolve the 180 degrees issue for you:

image.png.674f61c18a0bb1252f57cb0b2ebf0067.png

 

Note this is tuned to an  AM broadcast station.

 

 

  • Like 1
Link to post
Share on other sites
1 hour ago, kent_island_sailor said:

Not all radios have directional antennas. The directional antennas ares a ferrite rods wrapped in wire:

AM MF Aerial Ferrite Bar Rod Antenna DIY AM Radio KIT ...image.png.408878360a680c4cef6077c8ffb93d88.png

 

The null off the ends is quite sharp, just a few degrees ideally. The signal peak broadside to the antenna is very large, like 45 degrees, and is not used. Resolving the 180 degree ambiguity is a bit tricky. Some of these units have a second antenna to aid with that, but I never found it to be that accurate and usually you know where the beacon should be.

Airplanes have automatic direction finders that resolve the 180 degrees issue for you:

image.png.674f61c18a0bb1252f57cb0b2ebf0067.png

 

Note this is tuned to an  AM broadcast station.

 

 

I had one of those radios about 40 years ago, sorry I got rid of it. Was the days when Bass Strait had the three maritime D/F stations on the same frequency, transmitting one after the other.

 

Small portables invariably have an inbuilt ferrite rod. Some have external but they are becoming rare

https://swling.com/blog/2016/11/radios-with-rotatable-am-antennas/

 

The Tecsun 360 https://www.amazon.com/Tecsun-PL-360-Digital-Portable-Shortwave/dp/B004QJKO52 is still in production.

The 365 even comes with SSB https://www.anon-co.com/product/tecsun-pl365-ssb-radio

 

 

Link to post
Share on other sites