Chapter 4:
Imaging

4.1 Filters and Optical Elements

4.1.1 Nomenclature

4.1.2 Out-of-Band Leaks in NICMOS Filters

4.2 Photometry

4.2.1 Solar Analog Absolute Standards

4.2.2 White Dwarf Absolute Standards

4.2.3 Photometric Throughput and Stability

4.2.4 Count Rate Dependent Non-linearity

4.2.5 Intrapixel Sensitivity Variations

4.2.6 Special Situations

4.3 Focus History

4.4 Image Quality

4.4.1 Strehl Ratios

4.4.2 NIC1 and NIC2

4.4.3 NIC3

4.4.4 PSF Structure

4.4.5 Optical Aberrations: Coma and Astigmatism

4.4.6 Field Dependence of the PSF

4.4.7 Temporal Dependence of the PSF: HST Breathing and Cold Mask Shifts

4.5 Cosmic Rays

4.6 Photon and Cosmic Ray Persistence

4.7 The Infrared Background

4.8 The “Pedestal Effect”