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In article ,
says...
(Larry) wrote in message ...
How are you going to filter out white light from the stars? It
contains red and green, too.

I was imagining determining the difference in magnitude between the
red and green signals, 'though there are other possibilities for
differentiating between starlight spectra and nav light spectra.

If your boat is moving, you could well be on a collision course that
would allow you to see only the red or only the green light. That
makes the problem more difficult.

Furthermore, on a moonlight night, you will have to contend with
reflections off the wave tops. Those will have transient levels
of red and green that will complicate the detection problem.

Overall, it looks like this type of sensor would require quite a bit of
spectral discrimination and tracking intelligence.
What about coming up on the stern of that 950' containership at
anchor?

Unlikely mid ocean :-)

Better stick with the radar and get a shaft alternator or
wind bugger, instead.....please?

Well maybe, but what I've learned from this thread, my own
observations and others remarks is that nothing (including radar and
an alert watchkeeper) will detect everything which may cause a
problem.

.... Lucky for them it's a big ocean.

Indeed. But it really is a big ocean - I can recall three two week
stretches at sea when we saw absolutely no other vessels.

IIRC, on one crossing from Tahiti to LA, we saw no other vessels
at all. I suppose some may have popped up on radar, though, that
I didn't know about. Our radar had quite good range, too. But then
I was aboard a 400' missile range tracking ship at the time!

Mark Borgerson