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Eugene Grossman gives a very pleasant presentation of celestial navigation and why it's important to know.
This was for classical navigation before the advent of GPS or satellite systems.
Note: Sailors who use GPS at open sea are hundreds of miles out of range for cell phone towers.
Only satellites provide ephemeris data for GPS receivers to compute latitude and longitude on the globe earth.
Lots of sailing experience and much insight in his material.
Looks like this was recorded in 1972 or 1984.
The sun moves at 900 miles per hour over the earth's surface. We know this because it makes a full trip around the world every day, 24 hours a day (approximately). That makes 360 degrees divided by 24, which is 15 degrees per hour, and 60 Nm/d x 15 dph = 900 mph. Notice the duration of a day doesn't change from summer solstice to winter solstice.
Lots of facts here remind us none of this marine navigation works unless you recognize the earth is a globe.
Unlike GPS which you can use even if you deny the existence of satellites.
Your zenith distance measures global arc from your celestial position to the GP of the sun, in degrees.
Nautical miles east/west at the equator are one minute of arc, but closer to the south pole they're like they are close to the north pole, which is proportionally less than the number of feet a nautical mile is at the equator. The only way longitude distance can be less closer to the south pole is because the meridian lines get CLOSER TOGETHER near the south pole just like they do near the north pole, in other words, the earth is a globe.
Second half is Paul Miller's turn. He also has an easy-to-watch style of presentation.
A great circle measurement conceptually cuts the earth in half, i.e., the globe earth.
Celestial navigation allows the navigator to find out where you are even when you have no idea where you are.
Declination of the sun above the equator is an angular measurement from the center of the globe earth to the center of the sun.
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YouTube channel page gives outline of topics and times in the video:
Lecture 1 : Introduction to celestial Navigation Start
General Navigation Start at 02:55
Celestial Navigation start at 12:00
The Sextant 25:08
Sextant index error 28:44
Dip Correction 31:25
Sun Correction 33:38
Refraction & Parallax 35:17 -- Refraction correction necessary near the horizon because of false elevation of objects especially over the ocean.Time 39:32
LAN = Local Apparent Noon 48:47
Navigational Triangle 49:39
Refraction Correction and Parallax Correction provided as charts in the navigation tables. 1:25:30 ______________________________________________________________________________________
Lecture 2 : 53:30 Latitude & Longitude at Noon.