SkyMapper Filter Set: Design and Fabrication of Large-Scale Optical Filters

The SkyMapper Southern Sky Survey will be conducted from Siding Spring Observatory with u u , v v , g g , r r , i i , and z z filters that comprise glued glass combination filters with dimensions of309 × 309 × 15 mm 309 × 309 × 15 mm . In this article we discuss the rationale for our bandpasses and physical characteristics of the filter set. The u u , v v , g g , and z z filters are entirely glass filters, which provide highly uniform bandpasses across the complete filter aperture. The i i filter uses glass with a short-wave pass coating, and the r r filter is a complete dielectric filter. We describe the process by which the filters were constructed, including the processes used to obtain uniform dielectric coatings and optimized narrowband antireflection coatings, as well as the technique of gluing the large glass pieces together after coating using UV transparent epoxy cement. The measured passbands, including extinction and CCD QE, are presented.