Depending on your mathematical background, different resources may be more suitable: Astronomy: A Free, Online Astro 101 Textbook

A standard introductory course typically begins with fundamental physics and Earth-based observations before moving to the broader cosmos:

: Formation and dynamics of planets, moons, asteroids, and the Sun.

: Spherical astronomy, celestial mechanics (gravity and motion), and astronomical instruments like telescopes and spectrographs.

Introductory astronomy and astrophysics cover the observation and physical analysis of celestial bodies and the universe as a whole. While focuses on observing and cataloging celestial objects, astrophysics applies the laws of physics and chemistry to explain how these objects function, evolve, and interact. Core Concepts & Curriculum

: Understanding the electromagnetic spectrum, photometry, and how light reveals the temperature, mass, and composition of stars.