...and we whined about prices back in '75

higgs

higgs

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Aug 24, 2005
3,710
Nassau 34 Olcott, NY
18 years ago I bought a Nassau 34. It came to me with a berthful of all kinds of stuff from flashlights to a Davis plastic sextant. I put that sextant on a shelf thinking it would be cool to look into how to use it. It sat on that shelf for 18 years untouched. I sold the Nassau last weekend and was clearing out cabinets of boat parts and ran across the sextant. Looking through the instruction manual I found this flyer from Davis Instuments dated 1975.
 

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dLj

dLj

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Mar 23, 2017
4,414
Belliure 41 Back in the Chesapeake
Timm R Oday25 said:
Wow ..I wonder how many folks can actually use one now ..
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Many that could, now really can't. Or at least they would have to do a lot of practice to get back to a level of proficiency. GPS. It's amazing....

dj
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
23,159
CAL 35 Cruiser #21 moored EVERETT WA
I bought a Davis last year. The concept is easy. Shoot the SUN. Align the sun on the horizon by the use of the eyepiece and 2 mirrors… Now note the time. Consult the charts. Calculate the angles and …..
Maybe about 60 minutes later if your math is accurate, and you read the correct tables using the correct time and you have not shot yourself… You may find where you are in the world. With in a mile or so…Fine if you are on an ocean… Not so good to locate the Starbucks for a needed cup of caffeine. It is no wonder that GPS has become popular.
 
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kloudie1

kloudie1

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Nov 6, 2006
10,093
Hunter 34 Mandeville Louisiana
Back in 1991 on our first Gulf crossing to Isla Mujeres, we had Loran running and gave us really good position info. We had two sextants on board , one a Davis and the other a "real" one.. We did a couple of exercises to compare the two and compare to our real position from Loran. We found that the motion of the boat obliterated the differences in accuracy between the sextants.. We couldn't get any closer than 4-5 miles from the Loran reported position..which is fine for big open water.. sort of tells ya when to start looking for land. (the cocked hat was 8-10 miles across).. We were not (and still aren't) very good at using a sextant.
 
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smokey73

smokey73

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Oct 26, 2010
2,144
Hunter 40.5 Beaufort, SC
Sailed from Bermuda to Rhode Island on a Crysler Kiawa (I believe). We did running lines on the Sun with a sextant to get an approximate position. When we go close enough to pick up a radio signal we used a "radio direction finder." Basically a receiver with a directional antenna that looked like a bar on an old record player turntable. You rotated the bar looking at the signal meter to get the strongest reading, then plotted a line to the tower on the chart. You found another radio station frequency and did another and so on. Gave a location, most likely within about 5 miles or more. Once it was "land ho" it was all visual and plotting on a chart. Never gave it much thought about not getting to where we were heading.
 
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Justin_NSA

Justin_NSA

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Jul 7, 2004
8,492
Hunter 30T Cheney, KS
There was a movie about 20 years ago titled 'Longitude' about John Harrison who developed a marine chronometer that would win the Longitude prize.
 
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shemandr

shemandr

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Jan 1, 2006
7,591
Slickcraft 26 Sailfish
smokey73 said:
...When we go close enough to pick up a radio signal we used a "radio direction finder." Basically a receiver with a directional antenna that looked like a bar on an old record player turntable. You rotated the bar looking at the signal meter to get the strongest reading, then plotted a line to the tower on the chart. You found another radio station frequency and did another and so on...
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There used to be a network of radio beacons that you could sling together to use the RDF. I don't think they are operational now. On my Dad's boat in the 60's it wasn't that effective and as soon as Loran became available we switched to that. GPS was a few decades or so away.
I think the New England lobster fishermen were very adept at the RDF since they operated in fog and RDF was what they had. I would compare it to alchemy at that stage. My memory might fail me but I think you could use radio stations as well as the beacons. But there were several instances when we found Shinnicock Inlet with its use - not without some trepidation.
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
23,159
CAL 35 Cruiser #21 moored EVERETT WA
shemandr said:
I think the New England lobster fishermen were very adept at the RDF since they operated in fog and RDF was what they had. I would compare it to alchemy at that stage. My memory might fail me but I think you could use radio stations as well as the beacons.
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I think it was more like Witchery. Like divining for water. A little science and a little art. You are correct about the various radio towers providing a source of radiated energy to use. The best were high wattage radio stations that had their radio towers plotted on a chart near the coast. You could pretty easily dial in the frequency get a line on two or three and triangulate your position in a matter of minutes. Now a days all of that is hidden in black boxes and software. The principal is the same.
 
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