The COLREGs (as well as local supplemental rules) are rather complex. All of the additional items I listed are implicitly required at least for certain vessels in certain conditions.

All you "need" are the stars and some way to track time (a basic implementation conveniently provided by the sun). Everything else just increases accuracy. ;)

There was an interesting youtube video a while back on the SR-71 that could navigate via the stars years and years ago.

Of course the SR-71 probably never had cloud cover problems. :)

edit: I think this one: https://www.youtube.com/watch?v=tj9UwKQKE3A

The SR-71 also had an excellent clock on board.

> (a basic implementation conveniently provided by the sun).

No. You need an actual clock and charts. The sun and stars are completely useless for determining longitude without a clock.

The Moon on the other hand is marginally useful because its phases can be looked up. But its resolution is poor.

> The sun and stars are completely useless for determining longitude without a clock.

This is not completely true. The stars (and planets) provide for a very nice clock when viewed with sufficient resolution.