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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  • 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.

  • David Dolenc, Member

    I love sailing in the San Francisco Bay and greatly appreciate everything that MSC has to offer, the classes, clinics, club sails, racing and charters. I enjoy our supportive sailing community and use every opportunity to spend time on the water. After obtaining the certifications from MSC I did my first charter in Croatia in 2022 with my family. It was amazing and we’re looking forward to returning soon!

  • Andrew Goble, San Francisco

    It has been wonderful sailing with MSC over the years. Please extend my thanks to the owners, management, and staff for unrequited professionalism and high standards in a charter fleet. I have sailed with several in my years and none nearly hold a candle to the quality of business and staff at Modern Sailing.

  • Mike, Santa Rosa, California

    All of the courses and my instructors (JT and Stan) were extremely professional and full of knowledge and experience. I found I was able to learn from their experiences beyond the scope of the courses, and look forward to future opportunities to do so. I would highly recommend Modern Sailing to anyone.

  • 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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