Matthew 2:7

Then Herod, when he had privily called the wise men, enquired of them diligently what time the star appeared.

It was a secret conference, just fitting in with his political trickery. Had he made his inquiries in a public reception, his own courtiers might have become suspicious, but the unsuspecting visitors could be coaxed to talk freely in a private interview and would not become alarmed. The exact time of the star's first appearance was what Herod wanted, assuming probably that the birth of the child had occurred at the same time. All of which was an especially loathsome form of hypocrisy, an affectation of a kind interest in all that related to the Child in whose destinies the very stars seemed involved.