Sky and Telescope magazine provides a free Java-based sky chart that is very useful in planning your observations.

Of the deep sky objects on this chart, the following Messier Objects are your best bets when viewing in suburban areas in the northern hemisphere: M7, M8, M22, M24, M31, M41, M42, M44, M45 (The Pleiades) and M47. Also good bets are The Hyades and NGC 7000. Southern hemisphere suburban best bets are the Large and Small Magellanic Clouds, NGC 104, NGC 2070, NGC 2516, NGC 3532, NGC 5139 and The Coal Sack.SpaceWeather.com has current information on interesting viewing opportunities.

The best viewing is always in areas far from city lights. You can find dark sky areas using the National Atlas Map Maker. Choose "People", "Population" and click on the "Nighttime Lights" checkbox. Then push the "Redraw Map" button.

- Astronomy Picture of the Day
- The Hubble Gallery
- The Galex Image Gallery
- The Chandra Photo Album
- Images from the Spitzer Space Telescope
- The National Radio Astronomy Observatory
- SOHO: The Solar and Heliospheric Observatory
- The Solar Dynamics Observatory
- The 2 Micron All Sky Survey
- The Sloan Digital Sky Survey
- The THEMIS Mission Site
- The GLAST Mission Site
- The Planetary PhotoJournal at the Jet Propulsion Laboratory
- The Messier Objects at SEDS
- The Image Gallery at the Harvard-Smithsonian Center for Astrophysics
- The Image Archive at the European Space Observatory
- The Anglo-Australian Observatory

In addition, the home page for the Solar Data Analysis Center at NASA Goddard Space Flight Center includes current solar images in a variety of wavelengths.

NASA maintains a great deal of useful information about the Solar System. Information on minor bodies is available from the International Astronomical Union Minor Planet Center.

NASA also provides a wealth of information in

- Imagine the Universe
- Beyond Einstein
- Chronology of Lunar and Planetary Exploration
- NASA Eclipse Web Site
- NASA History
- The Remote Sensing Tutorial
- Galaxies and the Interstellar Medium

NOAA has a nice glossary of solar-terrestrial terms.

SIMBAD is an extremely useful portal for finding current scientific data on outer space objects. However, you must use accepted nomenclature for it to understand what you want.

Astronomy Answers: Positions in the Sky explains the math used to write programs such as the Sky and Telescope Sky Chart and the Solar System Viewer.

The University of Alaska Fairbanks Geophysical Institute has a good Aurora FAQ.

Universidad Complutense de Madrid maintains a very large list of Libraries of Stellar Spectra.

Lambda, the "Legacy Archive for Microwave Background Data Analysis", is "One Stop Shopping for CMB Researchers".

Our standard choice of parameters is based on the data set labeled "WMAP7+BAO+SNSALT" for the "ΛCDM" model.Here is a list of elementary particles from the Particle Data Group, who also publishes a review of astrophysical constants.

Here is a Periodic Table from Los Alamos National Laboratory. You can get information about isotopes from NIST, and from The Berkeley Laboratory Isotopes Project's Exploring the Table of Isotopes.

- absolute magnitude = 4.83 - 2.5 * log
_{10}luminosity_{solar} - absolute magnitude = apparent magnitude + 5 - 5 * log
_{10}distance_{pc} - acceleration
_{tidal}= G * mass_{1}* (1 / (distance - radius_{2})^{2}- 1 / distance^{2}) - angular momentum = 2 * π * mass * rotation rate * orbital radius
^{2} - angular resolution
_{arcsec}= .0025 * wavelength_{Angstroms}/ mirror diameter_{cm} - aphelion = semimajor axis * (1 + eccentricity)
- apparent wavelength / actual wavelength = 1 + recession velocity / c
- average molecular speed = 157 * (temperature / molecular weight
_{H = 1})^{1/2} - circumference of a circle = 2 * π * radius
- c = wavelength * frequency
- distance
_{parsecs}= 1000 / parallax_{milliarcseconds} - distance = velocity * time
- energy flux = luminosity / (4 π distance
^{2}) - energy = mass * c
^{2} - energy
_{eV}= h * frequency / e - escape velocity = (2 * G * mass / distance)
^{1/2} - force due to gravity = G * mass
_{1}* mass_{2}/ distance^{2} - horizon of a static black hole = 2 * G * mass / c
^{2} - light-gathering power ~ mirror radius
^{2} - line width = 2 * speed * central wavelength / c
- luminosity = 4 π σ radius
^{2}temperature^{4} - orbital period = 2 * π * (semimajor axis
^{3}/ (G * mass))^{1/2} - orbital velocity = (G * mass / distance)
^{1/2} - perihelion = semimajor axis * (1 - eccentricity)
- power emitted or absorbed per unit area = σ * temperature
^{4} - pressure = G * mass
^{2}/ radius^{4} - radians = π * degrees / 180
- recessional velocity = H
_{0}* distance - red shift = apparent wavelength / actual wavelength - 1
- red shift = scale factor
_{now}/ scale factor_{past}- 1 - size = distance * angular diameter
_{radians} - stellar lifetime
_{years}= 10^{10}mass_{solar}/ luminosity_{solar} - surface area of a sphere = 4 * π * radius
^{2} - temperature
- temperature
_{freeze out}= energy / k - volume of a sphere = 4/3 * π * radius
^{3} - wavelength of maximum thermal output
_{Angstroms}= 2.9 * 10^{7}Angstroms / temperature

Astronomical Unit (A.U.) | average radius of Earth's orbit | 1.496 * 10^{11} m |

speed of light (c) | 299,792,458 meters per second in a vacuum | |

electron volt (eV) | energy scale for electrons | 1.602 * 10^{-19} J |

Newton's Constant (G) | measure of strength of gravitational attraction | 6.674 *
10^{-11} N m^{2}/kg^{2} |

Hubble Parameter (H_{0}) | measure of rate of expansion of the universe | 69.9 km/s / Mpc |

Planck's Constant (h) | 6.626 * 10^{-34} kg m^{2} / s | |

Boltzmann Constant (k) | 1.381 * 10^{-23} J / K | |

solar luminosity (L_{S}) | 3.843 * 10^{26} W | |

solar mass (M_{S}) | 1.988 * 10^{30} kg | |

parsec (pc) | distance to a star whose parallax angle is one arcsecond | 3.086 * 10^{16} m = 3.262 ly |

solar radius (R_{S}) | 6.955 * 10^{8} m | |

Stefan-Boltzmann Constant (σ) | measure of strength of blackbody radiation |
5.67 * 10^{-8} W / m^{2} K^{4} |

absolute magnitude (M) | the apparent magnitude a star would have at a distance of 10 parsecs | |

acceleration (a) | rate of change of velocity | m / s^{2} |

Angstrom | measure of very small distances | 10^{-10} m |

angular momentum (L) | measure of how hard it is to change the rotation rate | |

angular resolution | angle subtending smallest resolvable details | |

aphelion | distance of farthest planetary orbital approach | |

apogee | distance of farthest lunar orbital approach | |

apparent magnitude (m) | same as apparent brightness; see visual magnitude | Δm = 1 ~ Δ brightness = 100^{1/5} |

arcsecond | 1/3600^{th} of a degree | |

blackbody | an perfect absorber and radiator of thermal radiation | |

celestial equator | plane of Earth's equator extended into space | |

centripetal acceleration | acceleration responsible for maintaining circular orbits | |

declination (dec) | celestial latitude relative to celestial equator | degrees, minutes, seconds |

Doppler Effect | difference between emitted and absorbed frequencies due to relative motion | |

electromagnetic radiation | electromagnetic waves emitted or absorbed by vibrating charges | |

electromagnetic waves | waves transporting energy through changing electric and magnetic fields | |

energy level (n) | a positive integer identifying an atomic electron's energy | |

frequency (ν) | number of wave cycles emitted per second | measured in Hz |

Hertz (Hz) | 1 Hertz = 1 cycle per second | |

intensity | power per unit area | |

Joule (J) | measure of energy | kg m^{2} / s^{2} |

Kelvin (K) | measure of temperature | Celsius + 273.15 |

kilogram (kg) | measure of mass | 2.2 pounds |

light-year (ly) | the distance light travels in a vacuum in one year | 9.461 * 10^{15} m |

luminosity (L) | total power output of a star | |

luminosity class | grouping of stars by absolute magnitude | |

meteor | bright streak that meteoroids make as they burn up in the atmosphere | |

meteorite | a meteoroid that survives the atmosphere to hit the surface | |

meteoroid | a small (< 100 m) piece of interplanetary debris; often found along the orbits of comets | |

meter (m) | measure of distance | 39.37 inches |

milliarcseconds (mas) | 1/1000^{th} of an arcsecond | |

Newton (N) | measure of force | kg m / s^{2} |

parallax | apparent change in position over 1/2 of a year | |

perigee | distance of closest lunar orbital approach | |

perihelion | distance of closest planetary orbital approach | |

power | energy per unit time | measured in Watts (W) = J / s |

radian | angular measure | 180 degrees = π radians |

red shift (z) | measure of cosmological distance | |

right ascension (RA) | celestial longitude relative to sun at vernal equinox | hours, minutes, seconds |

spectral class | grouping of stars by color | often includes luminosity class |

Tully-Fisher Law | galactic rotational velocity = 220000 * luminosity_{solar}^{0.22}, for 22000 Angstrom band | |

velocity (v) | rate of change of distance | m / s |

visual magnitude (v) | logarithmic function of intensity observed in the visual part of the spectrum | less for brighter stars |

wavelength (λ) | distance between successive wave crests |

©2012, Kenneth R. Koehler. All Rights Reserved. This document may be freely reproduced provided that this copyright notice is included.

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