Fringe Science: Defringing CCD Images with Neon Lamp Flat Fields

TL;DR

This paper introduces a simple, cost-effective method using neon lamp flat fields to effectively remove fringing in CCD images, improving photometric accuracy without extensive additional calibration time.

Contribution

The authors present a novel, inexpensive technique employing neon lamp flat fields to generate high S/N fringe frames for defringing CCD images efficiently.

Findings

Neon lamp fringe patterns match night sky emission lines.

The method produces high-quality fringe frames quickly.

It improves photometric accuracy in CCD imaging.

Abstract

Fringing in CCD images is troublesome from the aspect of photometric quality and image flatness in the final reduced product. Additionally, defringing during calibration requires the inefficient use of time during the night to collect and produce a "supersky" fringe frame. The fringe pattern observed in a CCD image for a given near-IR filter is dominated by small thickness variations across the detector with a second order effect caused by the wavelength extent of the emission lines within the bandpass which produce the interference pattern. We show that essentially any set of emission lines which generally match the wavelength coverage of the night sky emission lines within a bandpass will produce an identical fringe pattern. We present an easy, inexpensive, and efficient method which uses a neon lamp as a flat field source and produces high S/N fringe frames to use for defringing an image during the calibration process.