If you can visit the library in person, shelf-browsing is an excellent way to find books on your topic. Below is a basic guide to Library of Congress classification for astronomy.
LC Classification for Astronomy
QB140-237 Practical and spherical astronomy
QB349-421 Theoretical astronomy and celestial mechanics
QB468-480 Non-optical methods of astronomy
QB495-903 Descriptive astronomy
QB500.5-785 Solar system
QB980-991 Cosmogony. Cosmology