A useful website for students and amateur astronomers. Contains easy-to-follow tutorials on Observation, Science, Solar System, Stars, Our Galaxy, Cosmology, Astrobiology, Exoplanets and Astrophotography.
The Atomic Spectra Database contains data for radiative transitions and energy levels in atoms and atomic ions. Data are included for observed transitions of 99 elements and energy levels of 56 elements. Searchable by element and ion and gives you tables of each observed line or energy level of the relevant spectra.
"The Internet's Virtual Telescope”, displays an image of any part of the sky in any wavelength range desired. Searchable by coordinates or source name and provides the option of generating your image based on the data provided by a large selection of surveys.
Collection of databases hosted by the Strasbourg Astronomical Data Center which includes the SIMBAD database, containing information from the Catalog of Stellar Information and the Bibliographic Star Index, the ViZieR Catalog, which contains all information from the Astrophysical Virtual Observatory, an interactive sky atlas called Aladin, a dictionary and other useful tools.