Mishnah Rosh HaShanah 2:6-7.

    How do they examine the witnesses who come to testify about the new moon? They deal with them in order, as the pair of witnesses that arrives first they examine first.

     They bring in the greater of the two witnesses, and they say to him: Say how you saw the moon. Was it in front of the sun or behind the sun? To its north or to its south? How high was the moon over the horizon, and in which direction did it tilt? And how wide was it? If, for example, he said that he saw the moon in front of the sun, he has not said anything of substance, as this is impossible and therefore he is either mistaken or lying. And after they finish hearing the first witness’s testimony, they would bring in the second witness and examine him in a similar manner. If their statements match, their testimony is accepted and the court sanctifies the New Moon.

     And the court then asks all the other pairs of witnesses certain general matters, without probing into all the details. They do this not because they require the additional testimony, but so that the witnesses should not leave disappointed, and so that the witnesses should be accustomed to coming to testify, and will not hesitate to come the next time when they might be needed.

     After the witnesses have been examined and their testimony accepted, the head of the court says: It is sanctified. And all the people respond after him: It is sanctified; it is sanctified. Whether the moon was seen at its anticipated time, on the thirtieth day of the previous month, or whether it was not seen at its anticipated time, in which case witnesses are not necessary to establish the following day as the New Moon, the court sanctifies it and formally proclaims the day as the New Moon.