Difference between Starpath courses
Celestial Navigation (ASA 107) and Basic or Backup Celestial Navigation (ASA 117)

Cel Nav 107 is a full course on all aspects of celestial navigation, using all sights of all bodies. It uses the USNO version of the Nautical Almanac and NGA and NAO versions of Sight Reduction tables. At the end of the course you would know cel nav on the level of a professional ship master, and be able to find your position at sea to within about 1 to 2 nmi routinely following standard procedures. The course takes on average about one month to complete. The materials include 3 books: our textbook Celestial Navigation, The Star Finder Book, and the Starpath Celestial Navigation Work Forms.

Basic or Back up Cel Nav 117 is a much shorter course covering limited topics presented in a custom format that makes the short textbook (GPS Backup with a Mark 3 Sextant) a one book solution to cel nav position fixing. The only position fixes covered are Lat and Lon from midday sun sights, plus Lat by Polaris. The noon sights work any time of year in any ocean; the Lat by Polaris sights work only in the Northern Hemisphere about above 5°N. The sun sights are analyzed in a simplified form using a custom, perpetual sun almanac, good for any date and year. The Lat by Polaris sights are carried out using a custom procedure developed at Starpath that can be used any time Polaris is visible, any date, any ocean. The main text is oriented toward the inexpensive Davis Mark 3 sextant, but we include an additional textbook How to use Plastic Sextants: With Applications to Metal Sextants and a Review of Sextant Piloting, so students can follow through on the methods learned with any type of sextant. The 117 course takes on average about a week to complete, but there are no time requirements on either course. Position accuracy obtainable with the simpler methods is more like ± 5 to 10 nmi or so... and we just get a fix at mid day or a latitude at twilight.

Why 117 rather than 107?
There are two motivations for the shorter 117.

(1) The navigator wants to have a prudent back up to electronic navigation for ocean or coastal sailing, but does not have the interest nor time at the moment to study the full offerings of all cel nav.

(2) The navigator wants to pursue the ASA 108 Offshore Passage Making. Cel nav is a prerequisite for that courses, and the shorter 117 course meets that requirement. Thus again, if time is short and cel nav does not have a compelling interest at the moment, the 117 couse meets the need, and indeed provides the prudent back up to electronic navigation. Practice sights underway on ASA 108 can be taken in either format.

Is there any reason to take both courses?
From a practical point of view, maybe not. If there was good reason to take 117 in the first place, rather than 107, as outlined above, then those reasons would have to change to decide you want to learn more. It could be, however, 117 met the immediate needs, and now you have time or your interest has piqued, so you want to expand to learn more, then yes: 117 then 107.

On the other hand, if you have completed 107, then you know superior ways to do everything learned in 117, so you are not going to learn more accuracy nor versatility. On the other hand, you may want to teach others how to do cel nav in an efficient manner, and that you would learn in 117. None of the 117 techniques are solved in 107 the same way. Everything is simplified in 117 and the almanac data is also compiled in a more compact, easy to use form. We have less accuracy and versatility in 117 cel nav, but it is much faster and easier... and takes just one small book.