Quest for Longitude Celestial Navigation Week 2

Latitude Review Are the lines that circle the earth perpindicular to the equator. The equator is at a latitude of 0 The north and south poles are at a latitude of 90

Review of Calculating Latitude ► Various methods  Rule of thumb  Kamal  Backstaff  Cross staff  Quadrant ► Latitude only told you how far North or South you were ► What about east or west?

What is Longitude ► Prime Meridian ► Royal Observatory in Greenwich, England ► Sphere is 360˚ ► Longitude ranges 0-180˚ East or West of the Prime Meridian ► Positive longitude values are east of the Prime Meridian ► Negative longitude values are west of the Prime Meridian

Longitude As the World Turns ► ► The earth rotates every 24 hours. ► ► The earth rotates at complete 360˚ ► ► 360/24= The amount of degrees the earth rotates in 1 hour. ► ► How many degrees does the earth rotate in one hour? ► ► We will revisit this concept in a little bit.

Note on the Side ► International Date line is completely opposite of the Prime Meridian and is at 180˚ ► When it is noon along the prime meridian, it is midnight along the International Date Line.

Triangulation as a Tool ► On land, triangulation is fairly simple. ► Locate two points for intersection, three for triangulation. ► Apply basic principles. ► Locate three points ► Find bearings of all three points

Chip Log ► Check out this link ► at 3:25 minutes into the program ► Worth Watching ► Wooden block with a first 50’ not counted. ► When the line hits the marker the counter yells “CLEAR” ► The time 28 second sand glass is flipped. ► The counter counts the knots tied in the rope 48.3 inches apart in the 28 seconds. ► This is the speed of the craft. ► What would be possible problems with this method

Fathom That Fathom is a measure of depth somewhere around 6’. Now our nautical charts measure in feet not fathoms. Those are all those tiny numbers written on the nautical charts. How would these indicators help navigators?

Deduced Reckoning You Must Know these things to navigate. ► ► Starting Point – where you were. ► ► Course – what direction you are traveling. ► ► Speed – how fast you are traveling. ► ► Time – how long you have been traveling. ► ► Speed x Time = Distance

Vector Voyage ► Part 1  Let’s work through our Vector Voyage Worksheet Part 1

Not Enough! ► October 22, 1707 ► Isles of Scilly ► Board of Longitude Board of Longitude Board of Longitude ► Prizes were to be awarded to the first person to demonstrate a practical method for determining the longitude of a ship at sea. ► These prizes motivated many to search for a solution. £20,000 (millions) ► The Lunar Method was being considered as were the moons of Jupiter and the pattern of Venus.

Set and Drift and Leeway ► Set is the bearing in which the current is flowing ► Drift is the speed the current is flowing ► Speed, time, and angle make up leeway. ► 9fexA

Vector Voyage ► Part 2  Let’s look at the actual voyage.

Enter John Harrison ► Clock maker ► Took up the challenge to find an accurate measure of time on the seas. ► Spent 31 years working on this problem. ► Humidity, rough voyage, heat etc

H5 The Sea Clock or Chronometer

The Simplicity of Time ► John Harrison made it possible to calculate longitude by creating an accurate time keeper. ► You could compare the time difference to establish your longitude if your clock was set off Greenwich Mean Time. ► Example!

Longitude As the World Turns ► ► Quick review! ► ► The earth rotates every 24 hours. ► ► The earth rotates at complete 360˚ ► ► 360/24= 15 ► ► The earth rotates at 15˚ each hour

Earth’s Magnetic Pole ► The Geographic North Pole is different from the Axis of rotation ► It is different from the Geomagnetic North Pole ► This means that following magnetic north will not take you to the North Pole. ► This difference has a special name called Declination.

Working Declination ► Each map will show a declination value. ► ► This way you can calibrate your compass, which is pointing to geomagnetic north. ► ► You can make it point to the geographic north or True North. ► ► The geomagnetic pole is located 11 degrees of latitude from the geographic pole

Nautical Charts ► Nautical charts show the declination right on the map. ► Declination will alter slightly based on your location. ► We will cover more on this in next week’s lesson.

What is a Sextant? ► Simple tool that measures the angle between the horizon and one heavenly body. ► This information is then used with the Nautical Almanac to pinpoint your location.

How a Sextant Works ► If your sextant reading is taken at noon (the sun’s zenith) that will give you your latitude. ► If it is not noon, when your sextant reading is taken, you must note the exact time using a marine chronometer (really good watch set to Greenwich Mean Time). ► You will look up the time and sextant reading in the nautical almanac for the heavenly body you are using. ► Noon our time compared with noon Greenwich Mean Time, will give us 15 degrees of longitude for each hour. ► This will let you know where you are. ► We will explore nautical almanacs and charts a bit more in depth next week.

Nautical Almanac ► The Almanac specifies for each whole hour of the year the position on the Earth's surface in Greenwich Mean time and declination of the sun, moon, and stars. ► Remember that there are 57 selected stars for navigation. ► Using a nautical Almanac is in the next lesson as we find our location.

Final Notes ► Next week we will use the Nautical Almanac and Nautical Charts. ► Adjust our bearing for Declination based of the Chart. ► Use an orienteering compass to find and pin point our location in a coastal setting. ► We will use the sextant for a few examples, so please bring it with you next week. ► Do not use the sextant to look at the direct sunlight. I will try to get black and white silvered film for vision protection for next week. UV rays will cause damage to your eyes.

Making a CD Sextant Slide 1 ► This great activity is from the website linked below. Thank you! ► The website has a file for printing to scale the sextant markings on sticker paper. ►

Making a CD Sextant Slide 2 ► Gather up Supplies ► Print the scale on sticker paper ► Cut out the sextant scale. ► Be sure to set aside the vernier scale. ► Center extremely carefully over the center hole of the CD.

Making a CD Sextant Slide 3 ► Trim the center hole ► Place in Case, removing lid ► Remove the silver backing to one half (lengthwise of the mirror) of one of the mirrors

Making a CD Sextant Slide 4 ► Glue your legos to the mirrors ► Assemble your Sextant

Making a CD Sextant Slide 5 ► Calibrate with a distant focal point ► Dots on the wall. ► Then at zero add your Vernier scale

Using Your Sextant! ► /nav/CDSextantProject.ht m /nav/CDSextantProject.ht m /nav/CDSextantProject.ht m ► We will use and demonstrate our sextants using the full moon tonight. ► Place the view finder on the horizon ► Bring down the moon until it sits on the horizon.