How would Joseph Smith have guessed those in the Book of Mormon would have such detailed astronomical knowledge?

Those in the Book of Mormon claimed to know that planets move in a regular form. Alma 30:44 says:

But Alma said unto him: Thou hast had signs enough; will ye tempt your God? Will ye say, Show unto me a sign, when ye have the testimony of all these thy brethren, and also all the holy prophets? The scriptures are laid before thee, yea, and all things denote there is a God; yea, even the earth, and all things that are upon the face of it, yea, and its motion, yea, and also all the planets which move in their regular form do witness that there is a Supreme Creator.

Bruce E. Dale and Brian Dale explain why this is of interest:

Alma asserts that planets (not just one planet) “move in their regular form,” agreeing with Coe’s statement that the Maya knew the movements of Venus and Mars. For the Book of Mormon people to know that “a new star did appear,” they would have to know when and where the old stars would appear. So the correspondence is specific and detailed. It is also unusual. What Indian tribe of the American Northeast had any such detailed astronomical knowledge as that reported in The Maya?
– Bruce E. Dale and Brian Dale – Joseph Smith: The World’s Greatest Guesser (A Bayesian Statistical Analysis of Positive and Negative Correspondences between the Book of Mormon and The Maya)

Why would Joseph Smith have claim the ancestors of the Indians would know more about astronomy than their descendants?

See:

Bruce E. Dale and Brian Dale – Joseph Smith: The World’s Greatest Guesser (A Bayesian Statistical Analysis of Positive and Negative Correspondences between the Book of Mormon and The Maya)

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