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

TL;DR

This paper details the design, fabrication, and characterization of large-scale optical filters for the SkyMapper Southern Sky Survey, emphasizing uniformity, coating processes, and measured passbands.

Contribution

It introduces a novel process for constructing large glass filters with uniform bandpasses and optimized coatings for astronomical surveys.

Findings

Filters exhibit high uniformity across the aperture.

Successful application of dielectric and anti-reflection coatings.

Measured passbands align with design specifications.

Abstract

The SkyMapper Southern Sky Survey will be conducted from Siding Spring Observatory with u, v, g, r, i and z filters that comprise glued glass combination filters of dimension 309x309x15 mm. In this paper we discuss the rationale for our bandpasses and physical characteristics of the filter set. The u, v, g and z filters are entirely glass filters which provide highly uniform band passes across the complete filter aperture. The i filter uses glass with a short-wave pass coating, and the 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 narrow band anti-reflection 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.