I think we're probably distantly related; I'm descended from Margaret Watt b 16/12/1810 Tulliallan and m. John Ogilvie, another shipping family from the area. Their daughter Margaret Watt Ogilvie married my ship's master/owner ggggrandfather John Henderson, also of Tulliallan.
One way I've tracked John Henderson's travels is through Google Books - using Advanced Search and say the years 1820-1845 - and it throws up a lot of the Far East Journals that contain all the shipping travel to and from Asia. V. interesting. Cheers, Kate