A Circle and Semicircle Pattern

Photo date: December 27, 2019. Photographer: Mark Mahin.

I took the photos below while photographing only ordinary drops of pure, clean water falling in front of a black featureless background.  On this day one of multiple repeating patterns I got was one that consisted of a small circle to the left of a semicircle, both at the top of an orb.  Below are some examples:

Below is another example of the same pattern:

Below is another example of the same pattern:

Below is another example of the same pattern:

Below is another example of the same pattern:

Below is another example of the same pattern:

At about the 8:10 mark in the video below, you can see my camera viewfinder as I took photos with the pattern shown above.