I have just read Excalibur with great enjoyment. Please forgive a minor quibble; if it is any consolation you are by no means the first author I have read to fall into this error.
On page 205 you state “the sickle moon was low over the Southern hills” late at night (whatever that means).
A sickle moon occurs just before or after the New Moon. if it is the new moon it will be seen low in the West after sunset; if it is the old moon it will be seen low in the East before sunrise; it cannot be seen in the South – ever – nor in the middle of the night.
Strangely (to me!) authors worry about getting many other things right and forget to check their basic science.
Barry Landy