Optics and Detectors
Adaptive Optics - Adaptive Optics refers to optical systems which adapt to compensate for optical effects introduced by the medium between the object and its image.
Astronomical Spectroscopy - What is a Spectrum? How is a Spectrum Produced? What Does a Spectrum Tell Us? Learn about Modern Spectrographs and more.
Astrophotography & CCD Imaging - Eyeball observing is great, but say you want to capture views of the heavens for keeps? Here are tips on astroimaging with film, digital cameras, video cameras, and CCDs.
CCD Camera Applet - This Java Applet shows how a CCD camera works. The user can change the exposure time and image contrast.
CCD Observing Manual - This manual is a basic introduction and guide to using CCDs to make variable star estimates. The target audience is beginner to intermediate level CCD observers, although advanced CCD users who have not done any photometry will also find this helpful.
Concave and Convex Lenses - This site provides information about refraction and the Ray Model of Light for convex and concave lenses.
Concave and Convex Mirrors - This site provides information about reflection and the Ray Model of Light for flat, convex and concave mirrors.
How Digital Cameras Work - The key difference between a digital camera and a film-based camera is that the digital camera has no film. Instead, it has a sensor that converts light into electrical charges.
How Telescopes Works - Howstuffworks examines how a telescope works, discusses the various types of telescopes and takes a look at telescope mounts and accessories.
Photometers - Photometry is the science concerned with measuring human visual response to light.
Photometry - Photometry dates back more than 2,000 years to when the Greek astronomer Hipparchos divided the naked-eye stars into six brightness classes. Equations and history are provided at this site.
Spectroscopy - Check out these spectra of stars, galaxies, and nebulae.
Thin Lens Applet - Move the this lens around and see how it effects the paths of the light beams. More instructions are provided.
Galilean Refractors
Galileo's Telescope - The early history concerning the development of the first astronomical telescopes.
Making a Galilean Telescope - A Galilean telescope is defined as having one convex lens and one concave lens. The concave lens serves as the ocular lens, or the eyepiece, while the convex lens serves as the objective. Find out how to make this kind of telescope.
Refracting Astronomical Telescope - This Java applet simulates a simple refracting astronomical (inverting) telescope, consisting of two lenses which are called the objective and the eyepiece (ocular).
Refracting Telescopes - The direction of light propagation is changed at the boundary of glass and air by refraction. By designing lenses having the right curvature, this principle can be used to gather and focus light.
The Refractor - Most every-day telescopes and binoculars use lenses to gather the light which we see through an eyepiece. Astronomical telescopes that use lenses in this way are called Refracting Telescopes because the objective lens (at the end furthest from the eye) refracts the light to a focus which is magnified by the eyepiece.
Newtonian Reflectors
HERCULES - 41.2" Newtonian Telescope - The Hercules telescope project was begun in June 1994. It progressed off and on from then until it became an operational telescope in July 1996.
Reflecting Telescopes - The figures on this site illustrate the principle of reflection: the angle of incidence (measured from the perpendicular to the reflecting surface) is equal to the angle of reflection. The right side of the figure illustrates the use of a mirror to make a reflecting telescope.
The Reflector - The mirror of a reflector is at the bottom end of the telescope tube. It consists of a fairly thick, rigid disk of glass whose top surface has been accurately ground and polished so as to reflect all the light falling on it to a focus near the top end of the telescope tube.
William Herschel's 40ft telescope - William finished building his 40ft Newtonian reflector telescope in 1789 with grants totalling £4000 from King George III. It was the largest, most powerful telescope in the world and attracted visitors from far and wide. With it, William discovered the sixth and seventh satellites of Saturn and was able to resolve some globular clusters into individual stars.
Cassegrain Telescopes
Schmidt-Cassegrain - All of the professional telescopes built recently, from Hubble to Keck, are based on the folded Cassegrain design.
Schmidt-Cassegrain Telescope - The Schmidt-Cassegrain class of telescope (also called SCT) was named for the German astronomer Bernhard Schmidt and French sculptor Sieur Cassegrain. This hybrid telescope design has outpaced both the reflectors and refractors in the last decades to become the most popular telescope among amateur astronomers, especially among astrophotographers.
The Classical Cassegrain - In the classical Cassegrain telescope the primary mirror takes a paraboloid shape. This brings the light of any object in the field of the telescope to a focus near the top end of the tube, called the prime focus.
Twin Keck Telescopes - Learn more about the twin Keck Telescopes, the world's largest optical and infrared telescopes. Each stands eight stories.
Purchasing and Making
Amateur Telescope Makers - This site is a repository for information for and by ATMs (Amateur Telescope Makers). Learn how to grind you own mirror, build your own mount, and collimate your telescope.
Amateur Telescope Making - Longtime amateur telescope maker discusses the personal observatory, telescopes, grinding mirrors, and annoyances, and offers helpful advice.
Celestron - Celestron offers a wide range of telescopes, binoculars, spotting scopes, and optical accessories.
How to Build a Dobsonian Telescope - Learn how to construct a portable astronomical telescope. Features diagrams and photos of the telescope and expert advice from the San Francisco Sidewalk Astronomers.
Meade Instruments Corporation - Meade is a manufacturer of astronomical telescopes, CCD imaging systems, telescope accessories, binoculars, and microscopes.
Purchasing Amateur Telescopes FAQ - What you should know before you buy a telescope. This web site gives answers to Frequently Asked Questions (FAQ) about the types of telescopes, what accessories to purchase, and what you can hope to see with each telescope.
Radio Telescopes
National Radio Astronomy Observatory - The National Radio Astronomy Observatory (NRAO) unveils its new on-line image gallery. This gallery contains a collection of over 200 astronomical images made with NRAO instruments, as well as photographs of NRAO telescopes and facilities.
NRAO Very Large Array - The Very Large Array, one of the world's premier astronomical radio observatories, consists of 27 radio antennas in a Y-shaped configuration on the Plains of San Agustin fifty miles west of Socorro, New Mexico. Each antenna is 25 meters (81 feet) in diameter. The data from the antennas is combined electronically to give the resolution of an antenna 36km (22 miles) across, with the sensitivity of a dish 130 meters (422 feet) in diameter.
Radio Telescopes - Most of what we know about the Universe comes from information that has been carried to us by light. But we have seen that visible light is only a small part of the electromagnetic spectrum. In recent years the remainder of the electromagnetic spectrum has revealed extensive information about our Universe.
Radio Telescopes - Most radio telescopes work in the same way as an optical reflecting telescope except that the mirror is made of metal, which reflects the radio waves up to a detector at the prime focus.
The Very Large Array of Radio Telescopes - Drive about an hour west of Socorro, New Mexico, and you'll come across a scene that looks like it belongs in a science fiction movie. Large, white antennas are scattered across the landscape, pointed towards the sky.
Hubble Space Telescope
Amazing Space - An good set of web-based activities primarily designed for classroom use.
Astronomy Resources at STScI - Find out how you can use the Hubble Space Telescope through the Space Telescope Science Institute (STSci). NASA and The Space Telescope Science Institute (STScI) are pleased to announce a call for Proposals for Hubble Space Telescope (HST) Observations and funding for Archival Research and Theoretical Research programs.
Hand-Held Hubble - Make your own hand-held version of the Hubble Space Telescope! This Web site will show you how to make a scale model of NASA's Hubble Space Telescope out of parts you can find at local hardware and craft stores for under $20.
Hubble Space Telescope Public Pictures - Amazing pictures from the worlds most well know telescope. Images are organized by year and are provided directly from Hubble's home, the Space Telescope Science Institute. Images are accompanied by press releases.
Hubble Wallpaper - Use the images as a wallpaper for the desktop of your computer. Instructions are provided.
HubbleSite - News and Views - Check out the latest news and images from the Hubble Space Telescope. The site contains the most recent news releases.
The Hubble Space Telescope Project - Learn all about how the Hubble Space Telescope was built and upgraded. The Hubble Space Telescope orbits far above the distorting effects of the atmosphere, about 600 kilometers above the Earth. This perch gives astronomers with their clearest view ever, but it also prevents them from looking directly through the telescope. Instead, astronomers use Hubble's scientific instruments as their electronic eyes.
Chandra X-ray Observatory
Chandra News - This web page provides the latest news about the Chandra X-ray Observatory. New evidence from NASA's Chandra X-ray Observatory challenges an alternative theory of gravity that eliminates the need for dark matter — the elusive material thought to be the dominant form of matter in the universe.
Chandra Science - This web site has public information, inflight status reports, and press releases provided by the Chandra X-Ray Center (CXC) which is operated for NASA by the Smithsonian Astrophysical Observatory.
Spacecrafts
Apollo Program - This site contain dozens of NASA links concerning the Apollo program.
Cassini Spacecraft - This site offers significant events and mission status reports, plus more from NASA Jet Propulsion Laboratory.
Galileo Spacecraft - NASA mission to Jupiter. Learn about the Galileo spacecraft and its instruments.
Gemini Program - This site features goals, spacecraft, missions, movies, and more on the 2nd U.S. manned space program.
Mercury Program - This page offers images and information about the United States' first man-in-space program.
NASA Space Shuttle - This site contains orbiter facts, mission countdown and status, and other information.
Astronomy Software Collection
- Free SFA Star Charts
- Astronomy Orb
- Mars
- Jupiter
- Saturn
- SL9
- Eclipsing Binary Stars
- Color Science
- Astronomy JavaScript
- Movie Collection
- Stepper Motors