as i understand it, robotham witnessed an EXTREMELY rare weather/air phenomenon that made it possible to see a ship very far away, but both he and Tom ASSUMED that is NORMAL and that every other observer in the world is LYING/WRONG.
oh, and i remember reading about those "telescope made ship reappear" observations: the telescope in question was permanently mounted on top of a 100 foot high platform! so obviously it was the extra HEIGHT, not the telescope, that let them see it after it disappeared from the PERSPECTIVE of someone closer to sea level!