A modern variant of an ancient mariner celestial navigation technique called lunars is concisely explained by John S. Letcher in chapter 17 of his book Self-Contained Celestial Navigation with H.O. 208. If recovering time for a stopped chronometer ever becomes necessary this method offers a better than nothing means until a time signal can be received. Chapter 12 offers an additional more precise method of recovering time from a known position if time signals aren't available.
