The moon slides into a close encounter with the encircled planet Saturn this week. The chart shows the view looking east-south-east from London at midnight, as July 24 becomes July 25, shortly after the pair rises.
The moon will be a waning gibbous, 18.7 days old, and heading into its last quarter phase. It will have approximately 83% of its visible surface illuminated.
Saturn experiences retrograde motion, meaning that instead of moving steadily eastward night after night, measured against the background of stars, it appears to be retreating westward. By November it will have completed its loop and will move east again.
Of course, Saturn doesn’t actually do this, it’s an optical effect caused by the change in our perspective as Earth overtakes the outer planet and undertakes it. This year, the moment of enterprise, known as opposition, takes place on September 8.
Because of its apparent retrograde, Saturn remains locked in the constellation Aquarius, the water bearer, until later this year. The planet’s distinctly yellowish hue will be easily visible during this month’s conjunction because of its contrast with the moon’s silvery light.
The conjunction is also easily visible from the southern hemisphere on the same night.