Review long-slit spectrograph. Describe what images look like: star, sky, galaxy. Use APO 3.5m/DIS 000110 data as example.
Data reduction:
1. normal CCD processing: overscan, bias, dark, preflash.
2. flat fielding. Note problem that dome flats have spectral energy distribution of light source. ``Flatten'' the flats. Discuss slit illumination (note slit contribution) and methods for determining it (dome and twilight flats). (call specflat 44 53).
3. wavelength calibration. Basic principles. Caveats: line curvature, flexure (note skylines). (call read 40 43. call wavecal 40 41 43.)
4. flux calibration: correction for throughput as a function of wavelength. Not always required, e.g. if measured strengths relative to nearby continuum. Spectrophotometric standards, e.g. Massey et al. ApJ 328, 315 (1988). (call ./flux)
5. Object reduction: extracting object spectrum and sky spectrum. Aperture extraction vs. optimal extraction. Caveats: spectral curvature.