This is the publication quoted afaik listed on the British Museum site:
Mesopotamia and Iran in the Persian Period:Conquest and Imperialism 539 - 331 BC
Edited by John Curtis
1997; 246 x 189mm, 108pp
Illustrations: 17 colour, 53 black & white
Cased, ISBN 0-7141-1142-2, ,£16.99
If so then it covers the WRONG period and it would be interesting to see the full quote in context, ...so far can't find a readable version to find it though.
Oops already posted by Black Sheep, me so slow LOL (actually I had it all typed up ready then lost and and had to start again = not LOL)
Christopher Walker quoted appears to be an expert on ancient astronomy and is quoted in this context....