Cool. Good link. You are totally right about astrolabes (I was confusing them with sextants), however (I had to go back to the book for this) Hourani cites writings from the time of the Abbasid caliphate to the effect that they weren't used at sea because the rolling of the ships made them inaccurate, but were used on shore to determine the location of ports. The finger method was used while at sea.

As for the link between Indians and Polynesians, I'm fairly sure that you won't find anything. Guns Germs and Steel uses linguistic and archaeological evidence to show that the Polynesians developing their sailing technology on Taiwan and spread from there. That is a really long way from India. Also, I don't believe Indians or anyone else for that matter uses a navigation system similar to that used by Polynesians. However Indians and Polynesians could have come into contact when the Polynesians (Austronesians really, but related, and using the same boats and navigational techniques) spread from Sumatra to Madagascar around I think 500 AD. But, I still think it's not likely. The Indian Ocean trade at that time was apparently completely in the hands of the Arabs, and while there was definitely contact between Polynesian sailors and Arabs, they don't seem to have learned much from one another. Arabs sailed monohulls and steered by the sun, and Polynesians sailed cats (like us!) and steered by the moon.

If you haven't seen the website of the Polynesian Voyaging Society, your should check it out: http://pvs.kcc.hawaii.edu/welcome.html These are the guys that have preserved the old way of navigating, and still make long voyages between remote islands with no GPS and no compass. Pretty crazy.