ACS Anomalies SBC Optical Ghosts

SBC observations of bright objects may show optical ghosts possibly due to reflection between the back and front sides of the filter.

The brightness of the ghost is typically less than 1% of the star brightness. The displacement of the ghosts from the star image is filter dependent:

Filter	Displacement (pixels)
F122M	-50,+155
F125LP	-30,+95
F150LP	-28,+78

Note: Displacement from the center of the real object in the undistorted image.

The following images show two example for an isolated star:

and a cluster of stars(the ghost image is indicated with a red circle):