Introduction to Photometry Discipline: Education Photometry and CCDsPhotometry is a technique that measures the brightness of a star in an image. Each pixel on a CCD will have had a certain number of photons fall on it during an exposure. This number of photons translates to a number of electrons that are stored in the CCD until it is read out. The more photons hit a certain pixel, the more electrons will be stored there.Tags: brightnessphotometry
Brightness defined in more detail Brightness is described and measured in terms of radiant flux received from a celestial object. Radiant flux is the total amount of light energy (joules) that crosses one square meter per second. Radiant flux, F, is measured in watts. Radiant flux received from an object depends both on its distance, and on its luminosity. Luminosity is a measure of how much energy an object emits per second.
Comparing the magnitudes of different objects Discipline: EducationWhen Hipparchus first invented his magnitude scale, he intended each grade of magnitude to be about twice the brightness of the following grade. In other words, a first magnitude star was twice as bright as a second magnitude star. A star with apparent magnitude +3 was 8 (2x2x2) times brighter than a star with apparent magnitude +6.Tags: brightnesslogarithmHipparchusPogson
What is absolute magnitude? Discipline: Education Absolute magnitude is a concept that was invented after apparent magnitude when astronomers needed a way to compare the intrinsic, or absolute brightness of celestiaTags: brightnessparsecabsolute magnitude
What is apparent magnitude? Discipline: Education Astronomers use the term apparent magnitude to describe how bright an object appears in the sky from Earth. The idea of a magnitude scale dates back to Hipparchus (around 150 BC) who invented a scale to describe the the brightness of the stars he could see.Tags: brightnessHipparchus
Magnitudes and Distance Measurement Discipline: Education This guide describes magnitude, distance modulus and distance measurement. These concepts are central to understanding distances and scale in the universe. You will find that the text contains many links. Some will take you to a glossary definition, while others are links to more information about a topic you may want to explore further. Please use this guide in the way that makes most sense to you. You may want to read the entire guide first, then go back and follow links that interest you, or you may want to follow links as you go along. Tags: scalefluxbrightness
