Magnitude Systems is a very technical summary of filter systems with
links for professional observers.
Vision discusses the spectral response of the eye under normal and
low light conditions. It has useful diagrams.
Indices provides details and values for colour indices for different
spectral and luminosity classes of stars. It also gives values for specific
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
Reference Guides - Luminosity and Magnitude is part NASA's Cool Cosmos
site. It gives a simple, clear definition and discussion on each of these
Distance ladder - Spectroscopic Parallax gives a short set of points
describing how spectroscopic parallax works.
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
on the Net that also includes monthly sky charts.
Biography from the Department of the History and Philosophy of Science
at the University of Cambridge provides a concise, useful discussion on
of Photometry provides a useful one-page coverage of the key stages
in the development of photometric techniques.
the Stellar Magnitude Scale Works gives a simple, clear explanation
of the scale for the general public.
Astrophysics: Distance Ladder provides a clear description of how
spectroscopic parallax is applied and how it is used to determine stellar
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.
Astronomy: The Magnitude System is a concise page from the British
National Schools Observatory explaining the magnitude system for school
is a concise page of defintions for magnitudes, filter systems and photometry.
It includes a diagram comparing the wavebands of different filters.
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.
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.
Rods and Cones of the Human Eye is a clear concise explanation of
the phsyics of receptors in the human eye from the HyperPhysics
colour is the Sun? discusses the colour if the Sun and relates it
to colour theory. A technical page.
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.
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.
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.
Rays describes the Cosmic ray Air Shower Array at Louisiana State University
and has a handy section explaining how photomultiplier tubes work.
Reference Guides - Detector Arrays discusses the infrared CCDs and photometers
used on the Spitzer Space telescope.
of Photography in Astronomical Measurements gives details on the development
of astronomical photography from Daguerre, to hypersensitisation, Kodak emulsions
and plate "stacking".
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.
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.
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.
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.
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
Detectors starts with a clear explanation and diagram of how they work.
It gets a lot more technical as the article progresses.
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.
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.
Sources of Photometric Data
Database is a NASA database covering about 2,600 stars within 25 parsecs
- Standard Objects for Astronomy provides an extensive range of catalogs
for stellar photometric data.
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.
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.
Physlet is an effective Java applet that allows you to see the Planck
curve and colour for stars of different temperatures.
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.
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?
Photometry simulates measuring the brightness of different types of
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.
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.
Brightness Worksheet and Info is a simple page that can be printed
out with a set of questions and data for students.
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
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.
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.
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.