Autonomy is the big word in navigation right now. Both GPS and radar ranging (used in most NASA missions) rely on sending signals back and forth to an entity whose position is known (e.g. the earth, or a GPS satellite). To explore outside the solar system we need to navigate without such a reference. Station Explorer for X-Ray Timing and Navigation (SEXTANT) has already demonstrated the ability to get 10km precision. Our new method, Occultation X-ray Navigation (OXNAV), uses eclipses of distant objects to acquire positions, potentially with greater precision. SEXTANT and OXNAV complement each other and could be used to navigate autonomously. I will show promising results from serendipitous occultations in NICER, HEAO, and RXTE.