Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Magnitude Systems

  1. Jan 2, 2010 #1
    I didn't realize there are different magnitude systems.

    I have been doing an experiment on CCD extragalactic imaging and apparently I have been using values of magnitudes calibrated to the AB magnitude system. I noticed that my magnitudes were oddly smaller (numerically) that expected. Are my results wrong or have I been fooled by the AB system?
  2. jcsd
  3. Jan 2, 2010 #2


    User Avatar
    Science Advisor
    Homework Helper

    The difference between AB and Johnson magnitudes is pretty small.
    The filters you are using are unlikely to perfect match the response curve of either magnitude system
    The magnitudes were based on photographic emulsions which don't match the response of your CCD
    The atmopshere varies

    Basically - be suspicous of highly accurate magnitude figures unless the experimenter describes the calibration in detail
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook