WF/PC INSTRUMENT SCIENCE REPORT 90-02:
Filter F656N Anomaly - I
By Shawn Ewald
September, 1990
Abstract excerpted from the report:
The H-alpha narrow band filter in WF/PC-1, F656N, has deteriorated since delivery. A series of concentric rings is visible on exposures taken through this filter. The rings are centered near pixel (300,600) of CCD WF1 and extend across all four chips. Also, CCD WF4 shows fringes and filter F664N probably has a ghost.
The complete report (PDF 79 KB) is available.