Chapter 2 provides the "Fundamental Arguments" for the Sun and Moon (lunar perigee, node, etc.). These are polynomials of time (T). You need these to compute nutation and the equation of time.

: Moving away from the FK5 (Fifth Fundamental Catalogue) system to the International Celestial Reference System (ICRS)

Be careful when downloading scanned versions online. Many old links point to the 2nd edition.

The ESAA serves as a detailed companion to the Astronomical Almanac, offering insights into the mathematical and theoretical foundations of astronomical calculations. This supplement provides a thorough explanation of the algorithms, formulas, and techniques employed in the almanac's preparation, ensuring that users can accurately interpret and utilize the data. The ESAA covers a wide range of topics, from fundamental astronomical constants to complex calculations involving celestial mechanics and relativity.