G. A. Bottomley’s opinion concerning the determination of longitude by eclipses
Determining longitude by eclipses of the moon during the 1415-1418 voyages.
The Chinese lunar total eclipse method of determining longitude requires the moon to be visible at two widely separeted sites. The method is described in an appendix in ‘1421 – the year china discovered the world’.
“The 1415-1418 AD total eclipse moon viewing opportunities using sites then existing in the Indian Ocean and at Nanjing would extend Westwards to most of the Atlantic and North Polar regions; the Indian Ocean Eastwards to beyond the dataline and Antarctica; also the Eastern North Atlantic, half of the South Atlantic and North Polar regions. Only an East African coast station can link favorably with sites running far Westward from there. Partial ecipses may also be suitable as would eclipses earlier than 1415”.
“The location information comes from calculated moon altitudes (G.A. Bottomley). using eclipses predictions by Fred Espanek NASA GSFC.”
