Photometry Links

Photometry Theory

  • Astronomical Magnitude Systems is a very technical summary of filter systems with links for professional observers.
  • Color Vision discusses the spectral response of the eye under normal and low light conditions. It has useful diagrams.
  • Colour Indices provides details and values for colour indices for different spectral and luminosity classes of stars. It also gives values for specific stars.
  • Colour, Luminosity and Temperature is a set of problems with solutions for a British introductory-level university course on stars and galaxies. The level is comparable with HSC astrophysics though some questions are harder.
  • Cosmic Reference Guides - Luminosity and Magnitude is part NASA's Cool Cosmos site. It gives a simple, clear definition and discussion on each of these concepts.
  • Cosmological Distance ladder - Spectroscopic Parallax gives a short set of points describing how spectroscopic parallax works.
  • Distances is a page that discusses the distance to stars and relates this to their brightness. It has a useful diagram showing the relative brightness and distance of the stars in Crux and the Pointers. It is part of an excellent Australian educational site Astronomy on the Net that also includes monthly sky charts.
  • Hipparchus Biography from the Department of the History and Philosophy of Science at the University of Cambridge provides a concise, useful discussion on Hipparchus.
  • History of Photometry provides a useful one-page coverage of the key stages in the development of photometric techniques.
  • How the Stellar Magnitude Scale Works gives a simple, clear explanation of the scale for the general public.
  • IMSA Astrophysics: Distance Ladder provides a clear description of how spectroscopic parallax is applied and how it is used to determine stellar distances.
  • Magnitudes and Distance is an extremely useful set of introductory university-level notes that discuss apparent and absolute magnitude, distance modulus and interstellar reddening. It includes handy tables and shows how to apply formula to solve distance/magnitude problems.
  • NSO Astronomy: The Magnitude System is a concise page from the British National Schools Observatory explaining the magnitude system for school students.
  • Photometry is a concise page of defintions for magnitudes, filter systems and photometry. It includes a diagram comparing the wavebands of different filters.
  • Phy 445/515: Photometry is a concise but technical set of summary notes on basic photometry from a university-level course. it provides details on bandpasses, filters, magnitudes plus more specialised information.
  • Sky Publishing - The Stellar Magnitude System is a handy article written by one of the staff from Sky and Telescope Magazine explaining the concept of stellar magnitudes. Aimed at the general piblic and amateur observer.
  • Stellar Magnitudes provides a simple discussion of magnitudes before suggesting how you can visually determine the magnitude of satellites by comparing them to specific stars. It provides a finder chart with magnitudes for Crux. Also discusses use of binoculars.
  • The Rods and Cones of the Human Eye is a clear concise explanation of the phsyics of receptors in the human eye from the HyperPhysics site.
  • What colour is the Sun? discusses the colour if the Sun and relates it to colour theory. A technical page.

Astronomical Photography and CCDs

  • About Astronomical Photography is written by David Malin, formerly of the AAO and one of the world experts in developing innovative techniques in astronomical photography. You should also visit his page on Technical Stuff as well as his image archive at the AAO.
  • CCD Photometry is a very detailed page that discusses the theory and practical considerations required in using CCDs to measure stellar brightnesses. The background theory is useful as is the extensive discussion on filters.
  • CCD University is a set of technical pages leading you through different aspects of CCD construction and astronomical use. It is part of the Apogee site, a comapny that build CCD camears for a range of applications.
  • Comparison of Photos with Galileo's Drawings is an interesting site that provides details on Galileo's telescopic observations and drawings. It compares these with modern photographs through replica galilean telescopes.
  • Cosmic Rays describes the Cosmic ray Air Shower Array at Louisiana State University and has a handy section explaining how photomultiplier tubes work.
  • Cosmic Reference Guides - Detector Arrays discusses the infrared CCDs and photometers used on the Spitzer Space telescope.
  • History of Photography in Astronomical Measurements gives details on the development of astronomical photography from Daguerre, to hypersensitisation, Kodak emulsions and plate "stacking".
  • How Does a CCD Work? is a PowerPoint presentation from Swinburne University of Technology's Astronomy Online course that can be viewed online. It provides a clear description of how CCDs work and why they are valuable in astronomy.
  • Info about Super-Kamiokande provides a concise overview of what it is, how it works and what its purpose is. Also has a link to an image page.
  • Introduction to CCDs is an excellent page with a large number of diagrams and photographs. It uses the rain bucket analogy in a detaled but clear sequence of steps to explain how charge is accumulated and read out.
  • Molecular Expressions Microscopy Primer: Digital Imaging in Optical Microscopy provides detailed yet clear discussion of the quantum efficency and spectral response of CCDs compared with eyes and photographic film. It has a set of plots comparing them plus diagrams showing how frontside and backside illuminated CCDs work. It discusses how they operate in terms of semiconductor and photoeletric principles. Also provides a Java applet showing how photons interact with silicon.
  • Overview of CCD Detectors provides a clear historical background and description of the value of CCD detectors for astronomical use. Subsequent pages linked from this one discuss the advantages and disadvantages of CCDs and other useful information.
  • Phototube Detectors starts with a clear explanation and diagram of how they work. It gets a lot more technical as the article progresses.
  • Starizona CCD Guide - CCD Basics has several pages describing how CCDs work, how amateurs can use them for imaging, how CCDs compare with film for astrophotography and how images can be processed. Part of a commercial retailer's site.
  • The SNO Homepage provides details about the Sudbury Neutrino Observatory in Canada. The Detector page gives a well-illustarted explanation of how photomuliplier tubes are used to detect Cerenkov radiaition caused by neutrinos.
  • What CCDs are and how they work discusses the structure and physical principles behind a CCD including solid state physics. It highlights astronomical applications but also covers other uses.

Catalogs and Sources of Photometric Data

  • NStars Database is a NASA database covering about 2,600 stars within 25 parsecs of us.
  • SOFA - Standard Objects for Astronomy provides an extensive range of catalogs for stellar photometric data.
  • What color are the stars? is an unusual page that provides pixel rgb values that allow you to accurately portray the colour of the different spectal classes and many specific stars on your computer monitor. It also has useful links and discussion.

Applets, Activities and Software

  • Blackbody is a Shockwave applet that opens in your browser. By altering the temperature of the object you see the change in the shape and peak intensity of its Planck curve, the colour of the object and more. You can run this applet or online or download it to run on your own computer. It is part of an excellent series of physics and mathematics applets from PhET - Physics Education Technology and the University of Colarado. Visit the homepage to download this an other applets.
  • BlackBody Physlet is an effective Java applet that allows you to see the Planck curve and colour for stars of different temperatures.
  • Color and Stellar Temperature is an effective applet that allows you to compare the black body curves for two stars of different temperatures and determine their colours. You can add waveband filters and explore the infrared and ultraviolet parts of the spectrum as well as the visible.
  • Friends With the Universe distance and luminosity modules. There are three excellent activities available for download as zipped Word documents from the South African Astronomical Obsevatory's educational site. They are written by Case Rijsdijk, SAAO and use the inverse square relationship. To download, visit the site then click on modules 5, 7 & 8: The Inverse Square Law, Calculating the Power of the Sun and How far is that star?
  • Galaxy Photometry simulates measuring the brightness of different types of galaxies.
  • Interactions of Photons with Silicon is an interactive Java applet that shows how photons of different wavelength interact with silicon in a CCD. Accompanied by a detailed description.
  • Project CLEA: The Photoelectric Photometry of the Pleiades allows you to simulate control of a telescope to obtain photometric readings at different wavebands for the Pleiades open cluster. It is free software package for WinPCs that can be downloaded from the site. An extensive User guide and an excellent student book can also be downloaded.
  • Star Brightness Worksheet and Info is a simple page that can be printed out with a set of questions and data for students.
  • Stellar Magnitudes Applet is a simple applet designed for secondary students that relates the brightness of different stars to a varying number of light bulbs. It provides a link to a clear set of pages discussing properties of stars.
  • The Inverse Square Law is a Java applet that simulates photometer readings at varying distances form light bulbs and stars. You can produce flux vs distance plots for each situation.
  • Thermal Radiation Curves Applet allows you to specify a temperature or a peak wavelength for a star and view the corresponding Planck curve with a simulated visible spectrum superimposed on it.
  • Tutorial: Spectroscopic Parallax is a two-page pdf worksheet that allows you to work through the concept of spectroscopic parallax using examples. It has effective questions.