Astronomy, Piloting and Celestial Navigation

"Only two sailors, in my experience, never ran aground. One never left port and the other was an atrocious liar." Don Bamford, a Canadian author, sailor and boat builder cited in "The Boating Bible Manual of Seamanship" Wed, February 16, 2011 8:21 pm.

sextantIf you are out at night and the GPS goes down, you will need your Sextant to find where you are.   Portholes below will take you to information on your Astronomical and Navigational needs. Other links will take you to online access to Coastal US Nautical Charts.





American Practical Navigator NOAA -- Office of Coastal Survey - Online access to U.S. Coastal Nautical Charts
The Astrolabe - For those whose GPS goes down and whose sextant is broken. Great historical information SeaClear Navigational Software - a PC based chart plotter for Windows. With a GPS connected it displays the current position, speed, heading and other data on the screen. The chart is repositioned and new charts are loaded automatically as needed. Tracks may be saved to file for later reviewing and log book entries can be manually and automatically entered. Unlimited number of routes and waypoints can be created and used to assist the navigation. SeaClear is created for nautical navigation but can probably be used for other navigation needs.
Bowditch -The American Practical Navigator - The Authority Spherical Trigonometry, Celestial Navigation, and Great Circle Sailing
Celestial Navigation - Good Information United States Coast Guard - Online Inland and International Rules for Navigation
Celestaire - Good site for finding navigation equipment. WorldWide Telescope - See the wonders of the Universe with this downloadable program (and free) from Microsoft
Distance Calculations - Calculator for determining distances between two distinct points of latitude and longitude  
Magnetic Declination - From NOAA National Geophysical Data Center  
Marine Way  Points - A site with online viewing of Nautical Charts  
Modern Navigation - MIT Online Course  
National Geospatial Intelligence Agency - Maritime Safety  
Navigator Software - Download Navigation Software  


NAVIGATIONAL CHARTS: Want to see why updating your Navigational Charts is important? Check out Magnetic Declination Changes over time

Piloting and Navigation Mnemonics

Formula for converting compass headings back to true ones:

Chicago Dead Men Vote Twice At Elections:

Compass plus Deviation equals Magnetic heading.

Add the Variation to get the True heading. (Compass +/- Deviation = Magnetic +/- Variation = True Add East, Subtract West). (

In all of these corrections, "at elections" means Add Easterly deviations and variations as part of the calculation (and, by implication, subtract westerly ones).

Conversion of a True Directions or Courses to a Compass reading:

True Virgins Make Dull Companions Add Whiskey:

True plus Variation equals Magnetic heading. Beyond that, add the Deviation to get the Compass heading.

(True +/- Variation = Magnetic +/- Deviation = Compass Add West, Subtract East).

In all of these corrections, "Add Whiskey" means Add Westerly variations and deviations as part of the calculation (and, by implication, subtract easterly ones).

For additional mnemonics go to: Definitions and Mnemonics for Sailors and Powerboaters
Communications Applications -- Ariticle on Apps for Navigation, Weather and boating in general for the iPhone, iPad, Droid and Others. From "Mad Mariner" United States Coast Guard - Online Inland and International Rules for Navigation