General

• Windows to the Universe
• Astronomy Net
• Astronomy Resources -- Space Telescope Science Institute
• Astronomy Net Astroguide
• AstroWeb : Astronomy and Astrophysics on the Internet
• Astronomy HyperText Book
This is a part of a project called the Electronic Universe, which is " an educational outreach server at the University of Oregon maintained by Physics Professor Dr. Greg Bothun. It contains educational material and coursework for many sciences.
• The SAO/NASA Astrophysics Data System
"The SAO/NASA Astrophysics Data System (ADS) is a Digital Library portal for researchers in Astronomy and Physics, operated by the Smithsonian Astrophysical Observatory (SAO) under a NASA grant. The ADS maintains three bibliographic databases containing more than 6.7 million records: Astronomy and Astrophysics, Physics, and arXiv e-prints. The main body of data in the ADS consists of bibliographic records, which are searchable through highly customizable query forms, and full-text scans of much of the astronomical literature which can be browsed or searched via our full-text search interface. Integrated in its databases, the ADS provides access and pointers to a wealth of external resources, including electronic articles, data catalogs and archives. We currently have links to over 7.3 million records maintained by our collaborators."
• Encyclopedia Astronautica
• The Astrobiology Web
• Earth and Sky
• Spitzer Space Telescope
• Education Index: Astronomy Resources
• Leicester University Educational Guide to Space & Astronomy
• Physics and Astronomy Reference

Biographical Resources in Astronomy

• The Galileo Project
The Galileo Project is a hypertext source of information on the life and work of Galileo Galilei (1564-1642) and the science of his time.
• Astronomy Biography
• Eric Weisstein's World of Scientific Biography

Discussion Groups

• National Radio Astronomy Observatory Newsgroups
• Topica
• Catalist
• Tile.net
• Publicly Accessable Mailing Lists (paml.net)

Guides

• Que tal? in the Current Skies
• Abrams Planetarium Sky Calendar
• Sky and Telescope
• Calendar Zone: Celestial
Calendar Zone Celestial contains many calendars of astronomical events, such as: Calendar of the Moon, Calendar of the Constellations, Farmer's Almanac of Heavenly Details, calendars that show the positions of the planets, and so on

Historical Resources in Astronomy

• History of Astronomy Resources
• Open Directory: Astronomy History

Observatories

• The Astroguide Observatory Listings
• Palomar: California
• Royal Observatory Edinburgh
• Royal Observatory Greenwich
• Observatories of the Carnegie Institute of Washington
• National Solar Observatory: Arizona and California
• Griffith Observatory: Los Angeles
• Mount Wilson Observatory: San Gabriel Mountains, California
• University of California Observatories/Lick Observatory
• Astronomical Society of the Pacific: The Universe at Your Fingertips
• Russian Academy of Sciences: Institute of Terrestrial Magnetism, Ionosphere, and Radiowave Propagation
• Lowell Observatory: Arizona
• U.S. Naval Observatory
• National Radio Astronomy Observatory
• Hubble Telescope

Professional Organizations

• American Astronomical Society
• British Astronomical Association
• International Astronomical Union
• Astronomical Society of the Pacific
• International Dark-Sky Association (IDA)
• American Association of Variable Star Observers
• Space Telescope Science Institute
• Royal Astronomical Society of Canada
• Oklahoma Space Industry Developmental Authority

Periodicals

• Astronomy Magazine
• Bulletin of the American Astronomical Society
• Astronomy Now
• Astronomical Journal
• Sky and Telescope
• Information Bulletin on Variable Stars

Solar System

• Views of the Solar System: Hawaiian Astronomical Society
• The Nine Planets
• Solar System Live
• Earth and Moon Viewer
• Planetary Science Research Discoveries
• Views of the Solar System
• The Transit of Venus, June 2004

Space Exploration

• European Space Agency
• Institute of Space and Astronautical Science (Japan)
• Space Research Institute (Russia)
• SETI Institute

Stars and Galaxies

• Stars and Galaxies
• Journey Through the Galaxy
• Messier Catalog
• The Constellations Web Page
• National Geographic Star Journey
• The Constellations and their Stars
• Death Star
• Revised Catalog of Mk Spectra Types for the Cooler Stars

NOTE: While every effort is made to ensure the accuracy of these pages, errors may occur on occasion. Please verify any information obtained on these pages with the relevant department before relying on the information for anything critical.