GPS COMPUTER VS SEXTANT/ASTROLABE/Old ways/manual

[SmithDoor]

Interesting reading these posts.

Only partially related, I designed an Astrolabe back in 1993 (on Generic CADD) but it only got to the paper model stage (looks terribly beat up now). It was a PITA because I could not place text on a curve so had to do it letter by letter (or number) and in addition anticipate a vertical offset when the letter was printed. Like I said on my web page at the time I tested it in Canada with one plate and another in St. Lucia (I had plates for every 5deg) and in all cases it was bang-on accurate. What fantastic night skies in St Lucia! I even predicted a solar eclipse and that it would be a grazing partial. I was never able to get photogrametric plates made and lost the source design went I moved on to another job - it was on a work computer back in 1993.
http://surfin_dude.tripod.com/creative/astronomy/astronomy.html#Astrolabe

Previous to that, what got me interested in such things, was a 18” brass sundial design I did which, amongst a host of other things, tracked the sun’s progress across a map on it’s face thought each day and the course of the year. Tricky to etch an 18" dia - 3/8" thick plate or the 1/2" thick gnomen.
http://surfin_dude.tripod.com/creative/astronomy/astronomy.html#Sundial

Now, I keep it simple and use my “Yes V7” watch. Similar but better than the Prague astronomical clock. Used by NASA astronauts & Hollywood movie producers wanting to keep track of daylight. They have a successor to the V7 coming out soon. It will tell you sunrise/set, twilight, moon rise etc a whole host of other things after you program in your city (or manually if your city isn't on the infinitely long list).


No end of fun in this field!

How well dose it work?

Dave

Auto correct on my phone and forgetting to prof read .again

 

[jonpowers]

⫷⸻❋Conclusion❋⸻⫸ ​

.
The old about same century

1. Sextant is 10 minutes within 11 miles on the open ocean
2. Astrolabe is 15 minutes or within 17 miles on the open ocean

*** The Navy using some best today is within 1½ miles or apx 1 minute


Dave

I will comment based on sailing a 24 foot sail boat trans Pacific San Diego via the Pacific Islands to New Zealand: Given the low height of eye, height of waves on horizon and the motion of the sea way I always counted on a 30 (nautical) mile tolerance to produce a cocked hat position fix of Dead Reckoning, morning line of position and noon sight. I always found where I was going. The Polynesians were great travelers judging there position by the eye only estimate of height of celestial objects, based on using basket woven maps, said to be 1/2 degree precision same as I did with a sextant!

Jon

 

[SmithDoor]

I used new technology (home built CNC machine) to engrave this old technology. They look a lot cooler than a GPS chip.

I read about 40 years ago the first navigation tool was simple like astrolabe

I will comment based on sailing a 24 foot sail boat trans Pacific San Diego via the Pacific Islands to New Zealand: Given the low height of eye, height of waves on horizon and the motion of the sea way I always counted on a 30 (nautical) mile tolerance to produce a cocked hat position fix of Dead Reckoning, morning line of position and noon sight. I always found where I was going. The Polynesians were great travelers judging there position by the eye only estimate of height of celestial objects, based on using basket woven maps, said to be 1/2 degree precision same as I did with a sextant!

Jon

Thank you

I was told about same over 50 years but think did I hear that right. So nice hearing again to refresh my memory.
I always remember high noon then dead reckoning till high noon .
I could remember from old western movie everthing happened at high noon.

It nice reading my background is in Aviation and need location almost real time nere mountains. Dead reckoning is used a lot but still needing information faster.

Thank you for sharing
Dave