C e l e s t i a l N a v i g a t i o n Ship 609 Sea Explorers - BSA Edward S. Popko

History of Celestial  Oldest Form of Land / Sea / Air Navigation  Early Records Date to 1500BC  Used by Arabs for Desert Crossings  Kamal and Astrolabe  Used in Oceania / Polynesia for 1000 Yrs  Used in Gemini, Apollo, Shuttle Programs  Backup on all Military Ships & Aircraft  Long Line of Incremental Improvements  Sextant: Based on John Davis’s Backstaff 1590  Time: John Harrison’s Ocean Going Chronometer 1735  Math and Procedures: Nathaniel Bowditch 1838  LOPs: John Sumner 1875

Why is Celestial Important?  Essential to Survival at Sea  Critical Backup to Electronic Navigation  Insurance for “Lazy” Piloting and DR Work  Very Useful in Coastal Navigation  Distance Off  3 Point Fix  Collision Avoidance  Required in Some Sailing Events (Marion/Bermuda..)  Pure Enjoyment  Applied Astronomy  Backpacking/Recreation  Key to History of Ships, Commerce, Warfare, Discovery, Applied Astronomy

What is Celestial Navigation  Exploiting the Regular Motions of Stars and Planets to Determine Where You Are  Every Sighting with a Sextant Results in a Line of Position (LOP)  Lines of Position can be Plotted on a Chart You Are Somewhere on That Line!  The Intersection of Two or More LOPs results in a fix

What Do You Use if For?  Locating Lines of Position, Establishing FIXs  Checking your Speed & Course  Determining Effects of Current and Wind on Boat  Calibrating your Compass

What Do You Use if For?  Locating Lines of Position, Establishing FIXs  Checking your Speed & Course  Determining Effects of Current and Wind on Boat  Calibrating your Compass  Map Making  Backpacking / Survival  Distance-Off  Collision Avoidance  Basic Astronomy

Basic Theory  Every Celestial Body has a Ground Point - GP  You Measure Angle of Body to Horizon  Assume a Location  “Reduce the Sight”  Compare Computed and Assumed Location  Plot Results Every Sight Results in one LOP on your Chart!  Look at the Sun, Moon, Planets & Stars

What Stars Tell Us Every Celestial Body has a Ground Point - GP Sextant Angle GP Nautical Almanac had GP for all times every day

Taking a Sight What Time is it? What Angle is it? What Body are we Looking at? Sextant Measures Angles - Nothing More!

Basic Procedure  Identify Celestial Body  Measure it’s Height above the Horizon (Sextant)  Time Exact Moment of Sighting  Use Nautical Almanac to find Ground Point of Body  Assume a Position  “Reduce the Sight”  Plot Resulting LOP and Azimuth on Chart  Update Dead Reckoning

A “Celestial Day’s Work”  Morning Twilight Stars for a Fix  Mid-Morning Sun / Moon / Venus  Noon Sun (for Latitude)  Mid-Afternoon Sun / Moon / Venus  Evening Twilight Stars for a Fix  Special LOPs  Coarse  Speed  Longitude  Latitude (Local Noon)  Course Plotting, DR Updates, FIX, Other

What do You Need? Accurate Watch (You have one)  Sextant (a $20 plastic sextant is fine) Large Lake or Ocean View or.....  Dish of Water or Old Motor Oil (All are Free) Makes Artificial Horizon  Nautical Almanac (Must have - $5- get at boat stores) Small Area Plotting Sheet ( Draw your own chart) Drafting Items.. Pencils, Protractor (You have them) Optional Items (You have them) Calculator Star Guide from Astronomy Magazine or Newspaper You already have most of the stuff you need.

Demonstrations  A Two Day Boating Cruise  Finding The Camp Site at a State Park (Landlocked)

Fix from Two LOPs C 075 S FIX

What Limits Celestial  Must have Clear View of Horizon  Limited Dawn and Dusk Star Fix Window  Using Sextant from Small Pitching Boats  Weather and Sky Visibility  Dawn / Dusk / Daytime Only

How Do You Learn it?  Read Boy Scouts’ “Sea Exploring Manual”  Try Astronomy Merit Badge  Visit a Planetarium (Mystic Sea Port, Haydan...)  Take an Off-Shore Navigation Cruise  Ocean Star from Ocean Navigator Magazine  Teach Yourself in the Back Yard  Plastic Sextant + Artificial Horizon + Back Yard/Camping Site  Take a Class  U.S. Power Squadron. Coast Guard, Marinas etc.  Attend a Boat Show Clinic  Read Astronomy Magazines  Visit a Maritime Museum

What is New after 1500 Yrs.?  Inexpensive Calculators that do all the Math  High-Tech Sextants  Composite Plastics  Very High Quality Mirrors / Scope Optics / Filter Design  Built-in Clocks and Sight Log Memories  Artificial Horizons - Can Sight from Land or at Night  Night Vision Telescopes - Can Sight all Night  Automatic Azimuth/Compass Units  Celestial & Star Calculators  Links to PC Navigation and DR Plotting  Applications in the Space Program  Shuttle, Hubble, “Guide Star” Projects  PC Simulators

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