When I use my Apple Pencil with Photoshop clone tool or healing tool my iPad shows a faint red ghosting or halo where the pencil touches. I don't remember seeing it when I first started using Astropad. I updated to Maverick and even uninstalled/installed Astropad both on iPad and MacBook Pro. The pencil is fully charged. It's a mystery.
Update: It does happen around dancing ants.