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Sailing in the bay towards the Bay Bridge and San Francisco

ASA 107

Celestial Navigation

Master the art that aided all those who followed Columbus across the oceans of the world. Celestial Navigation continues as a back up for serious navigators and for ocean cruisers. The game - how close can you get comparing other forms of navigation including the GPS. The purpose - When a GPS fails, be ready to work out courses to your destinations on your own. ASA - has both a short and long version of the Celestial course.


This robust celestial navigation class teaches the theory and practice to determine latitude and longitude at sea using the stars, planets, moon and sun. You will learn the same methodology utilized by the post WWII U.S. Navy, Coast Guard, Merchant Marine and Air Force.

4 Days or 2 weekends

Member: $745

Non member: $895

What's Included

Find a date that works for you

Need a different date? Give us a call (510) 535-1954

Before the Course

What to expect

Schedule and Details:

  • Meet at Afterguard Sailing Academy, 1285 Embarcadero (Oakland CA 94606)

  • This is four day or two weekend Course spent in the classroom. 

  • The written exam is at the end the of the class.

Additional info:

There are bathrooms at our facility and on the boats. Please make sure to check in with your teacher about how to use the 'head 'on the boat, before leaving the docks!

ASA 107 - Course Description

Able to apply celestial navigation theory and practices for safe navigation of a sailing vessel in offshore waters —

Find a date that works for you

Great course for an introduction into sailing in the bay!

This was the perfect way to become comfortable with sailing. By the end of the course I was confident in all the terminology and functions of the boat and understood how to make adjustments to the sail. I look forward to more time on the water with Afterguard!

Hannah R. (ASA 101 course July 2023) 

What's covered in the ASA 101?


1. Convert longitude into time.
2. Convert standard time and zone time to GMT and vice versa.
3. Calculate the zone time given longitude.
4. Calculate the chronometer (or watch) error given a previous error and the daily rate.
5. Apply corrections for index error, dip of the horizon, and total correction to convert sextant altitudes of the sun, stars, planets, and moon to true altitudes.
6. Calculate the time of meridian passage of the sun and calculate the boat’s latitude from the observed meridian altitude of the sun.
7. Determine the latitude at twilight by means of the Pole Star.
8. Solve the navigational triangle using a navigation table and show all appropriate work.
9. Plot celestial lines of position on a Mercator projection or on a universal plotting sheet.
10. Calculate the times (ship’s and GMT) of sunrise, sunset, and twilight.
11. Determine the approximate azimuths and altitudes of the navigational stars and planets at twilight.
12. Calculate and plot the lines of position obtained from observations of several celestial bodies at twilight to find the boat’s position.
13. Advance the LOP obtained from a sun sight to another LOP obtained from the sun at a later time and find the boat’s position using a running fix (sun-run-sun).
14. Calculate the true bearing of a low altitude celestial body to determine the error and deviation of the compass.


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