1,314. Calculating the Actual Position of the Moon

Hilchos Kiddush HaChodesh 15:4

After calculating the angle of the proper course, proceed as follows: if the result is smaller than 180 degrees, subtract the angle of the course from the average of the moon at the time of its sighting. If it’s greater than 180 degrees, add the angle of the course to the average of the moon at the time of its sighting. The result of this operation is the actual position of the moon at the time of its sighting.

Hilchos Kiddush HaChodesh 15:5

If the proper course is exactly 180 or 360 degrees, there is no angle of the course. Rather, the average position of the moon at the time of its sighting is also its actual position at that time.