ASA 117 Basic Celestial Endorsement | Modern Sailing

ASA 117 Basic Celestial Endorsement

2 days, 9:00am - 3:30pm

Embark on a journey to learn the age-old techniques of celestial navigation, a fundamental skill that connects mariners to the vastness of the cosmos and the traditions of seafaring. While modern vessels are equipped with sophisticated electronic navigation systems, the ability to pinpoint your position using the sun, moon, planets, and stars offers self-reliance and seaworthy preparedness. 

The ASA 117 course introduces sailors to the timeless art of celestial navigation using a sextant and celestial bodies to determine position at sea. This course is designed for those interested in gaining a foundational understanding of how to navigate offshore without relying on GPS or electronic tools. 

What You'll Learn:

  • Basic concepts of celestial navigation
  • Use and care of the sextant
  • How to measure the sun's altitude
  • Use of the Nautical Almanac and sight reduction table
  • Determining latitude and longitude by sun sight
  • Understanding time, time zones, and GMT
  • Plotting lines of position (LOPs) on a nautical chart

Your Celestial Endorsement textbook, GPS Backup with a Mark 2 Sextant by David Burch, is included with the purchase of your course and will be mailed to you. If you prefer to pick up your course materials in person or if you signed up less than a week from the first day of your course, please contact our office. Advance study of these books will enhance your success in this course.

Enroll in ASA 117 to equip yourself with this essential skill. If you're interested in a deeper dive into celestial navigation, look for our ASA 107 Celestial Navigation course, typically scheduled during the fall and winter months.

The ASA 117 certification serves as a prerequisite to ASA 108 Offshore Passagemaking.

There are three ways to sign up for this course - by phone (415) 331-8250, email, or by clicking the link below.

View Schedule & Sign Up

Cost for Members: 
$560
Cost for Non Members: 
$745
Prerequisites: 
ASA 105 Coastal Navigation
Capt. Steve Matles using sextant

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  • Esther C

    I took ASA 101 with them recently. They have the best customer service I've ever seen! I mistyped my address when I signed up online so didn't receive the textbook. I called and the lady immediately sent me another copy! Everyone at the club is super friendly.

  • John Boynton

    The class was terrific. I know you must get many compliments about your sailing instructors...But I must tell you that Robert is outstanding. Having taught SCUBA, I really appreciate the way he is so sensitive to all on board, dealing with each so well, knowing quickly their strengths and weaknesses making each feel special and cared for.

  • Salesforce (Ashley H.)

    Our team at Salesforce did the Corporate Regatta Team Buidling activity (August 2026). What a blast!! HIghly recommend for your next team activity. It's fun to be out on the water, but the skippers also did a great job of teaching us all the sailing basics. The race is set up well so that we all had a chance to try out different roles. We did it with 11 people across two boats but having more boats is also doable and would lead to even more competition.

  • Warren Leiden, Member

    I try to get out on the water every week: out the Gate, around Angel, up Raccoon - I love it all. After 18 years as a member of OCSC in Berkeley, I learned to sail the bigger boats at Modern by taking ASA 103 and 104. My ASA 104 instructor Dave Russell was terrific. Also, Captain Bill Moreland has been very generous in giving informal advice whenever I’ve asked him. Thanks to Bill, I no longer have any anxiety about docking!

  • John Kratochvil, Oregon

    I would like to compliment Stan Lander for his coaching, counseling and teaching Heavy Weather Offshore Sailing. Stan was very accommodating to all of the student's interests and shared his many years of insight on handling the boat in heavy seas. I would certainly recommend Stan and this course to sheltered waters sailors. My confidence in handling a boat of this size was certainly enhanced by the experience.

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