Introduction Astronomy Tools Concepts 1. Electromagnetic Spectrum 2. Atmosphere Limitations 3. Space Observations Equipment 1. Telescopes 2. Radio 3. Space Tools 4. Photography 5. Spectroscopy 6. Computers 7. Advanced Methods 8. Radio Astronomy Basic Mathematics Algebra Statistics Geometry Scientific Notation Log Scales Calculus Physics Concepts - Basic Units of Measure - Mass & Density - Temperature - Velocity & Acceleration - Force, Pressure & Energy - Atoms - Quantum Physics - Nature of Light Formulas - Brightness - Cepheid Rulers - Distance - Doppler Shift - Frequency & Wavelength - Hubble's Law - Inverse Square Law - Kinetic Energy - Luminosity - Magnitudes - Convert Mass to Energy - Kepler & Newton - Orbits - Parallax - Planck's Law - Relativistic Redshift - Relativity - Schwarzschild Radius  - Synodic & Sidereal Periods - Sidereal Time - Small Angle Formula - Stellar Properties  - Stephan-Boltzmann Law - Telescope Related - Temperature - Tidal Forces - Wien's Law Constants Computer Models Additional Resources 1. Advanced Topics 2. Guest Contributions
 Concepts - Space Observations While radio waves, near-infrared (near-IR), and visible light are observable from surface of the Earth, we need to introduce tools into space to observe other frequencies of the EM-band. This section will introduce: In order to see the small window of the near-IR spectrum from the ground, some novel approaches have been designed and implemented. Viewing of the near-IR is possible only by: Very high altitude Using super-cooled CCD imagery Mirrors using silver or gold coated mirrors Small secondary mirrors Cooled telescope tubes and housings of mirrors along the optical path An example of an infrared optimized telescope is the Keck Observatory Gemini-North telescope. Back to Top Infrared: To view the residual IR spectrum, high altitude observatories - or orbiting satellites - are required. Another method is to observe from Antarctica - if you like the cold! There are two in-flight observatories: In addition, the following observatories are (and were) in orbit around the Earth: Infrared Astronomy Satellite (IRAS) Midcourse Space Experiment (MSX) The Hubble Space Telescope's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) The Spitzer Space Telescope (SST) Back to Top X-Ray: This high-energy portion of the EM-band is only visible from space. Between 1949 to 1962, sounding rockets traveling up to 100 km above the surface would carry Geiger counters to measure X-ray emission. A sounding rocket is nothing more than a standard rocket with the Geiger counter and other related electronics housed in within the nose. By 1970, several orbiting X-ray observatories would begin capturing valuable data. These include the following observatories: Objects observed by X-ray are (but not limited to) supernova remnants, accretion disks, pulsars, and black holes. Back to Top Ultraviolet: The ultraviolet (UV) region of the EM-band allows the study of very hot, young stars. Additionally, populations of young, hot stars within the disks of spiral galaxies are within easy view of a UV telescope. This also requires satellite observatories. Here is a list of UV observatories: Orbiting Astronomical Observatory (OAO-2) - the first UV observatory, 1968 Copernicus (OAO-3) International Ultraviolet Explorer (IUE) Ultraviolet Imaging Telescope (UIT) Hopkins Ultraviolet Telescope (HUT) Extreme Ultraviolet Explorer (EUVE) ROSAT Wide Field Camera (WFC) Hubble Space Telescope's Goddard High Resolution Spectrograph (GHRS) Hubble Space Telescope's Faint Object Camera (FOC) Hubble Space Telescope's Space Telescope Imaging Spectrograph (STIS) Far Ultraviolet Spectroscopic Explorer (FUSE) Back to Top Gamma Rays: Gamma rays are the highest energy radiation resulting in extremely short wavelengths. Sources of gamma rays are supernovas, neutron stars, intense gravity regions and active galaxies (galaxies with a large and active black hole at the center). Here is a list of some gamma ray satellites: