Intro to HST Data Handbook
The Introduction to the HST Data Handbook contains information that is relevant for analyzing data from all of the HST instruments, past and present, and replaces the "Introduction to Reducing HST Data" and appendixes of the WFPC2 Data Handbook below.
WFPC2 Data Handbook
The WFPC2 Data Handbook (v5.0) is the primary reference for data format and analysis information. The introductory section, "Introduction to Reducing HST Data", and the appendixes found in the WFPC2 Data Handbook have been updated and should be accessed via the link above.