NavList:

Something to keep in mind about iteration is that "lines" of position generally cross each other twice.  If you're working with only two lines, you actually have two equally valid fixes.  An iterative process will typically converge on the one that's closest to your initial guess.  (It can be fun to deliberatley "guess" your antipode and see where the process puts you.)

Absolutely any information you have on the azimuths of the two bodies is usually enough to work as a sanity check here.  For example, if your sun-moon fix has the sun on the right and you distinctly remember it being on the left, you've arrived at the wrong fix.