Chapter 9:
WFC3 Exposure-Time Calculation

9.1 Overview

9.2 The WFC3 Exposure Time Calculator (ETC)

9.3 Calculating Sensitivities from Tabulated Data

9.4 Count Rates (Imaging)

9.4.1 Point Source

9.4.2 Diffuse Sources

9.4.3 Emission-Line Sources

9.5 Count Rates (Slitless Spectroscopy)

9.6 Estimating Exposure Times

9.6.1 S/N Reached in a Given Exposure Time

9.6.2 Exposure Time to Reach a Given S/N

9.6.3 Exposure Time Estimates for Red Targets in F850LP

9.7 Sky Background

9.7.1 Background Variations and LOW-SKY

9.7.2 Geocoronal Emission and SHADOW

9.8 Interstellar Extinction

9.9 Exposure-Time Calculation Examples

9.9.1 Example 1: UVIS Imaging of a Faint Point Source

9.9.2 Example 2: IR Imaging of a Faint Extended Source

9.9.3 Example 3: Imaging an HII region in M83 in Hα