1. Flux Density
Spectral Energy Density

2. Apparent Magnitude Ancient Greek Astronomers
Visually determined brightness of stars
Brightest - Magnitude 1
Faintest Star visible to the nnaked eye - Magnitude 6

3. Photmetric Magnitudes
Filters
Johnson UBV Bands
Zero Point Set using Vega

4. Apparent Magnitude
Zero point?
Magnitude difference of 5

5. Absoulte Magnitude
Intrinsic Property
of the Source –
Luminosity

6. K correction
Distance Modulus

7. Bolometric Magnitudes
Sometimes the band is sufficiently broad
to allow the entire radiation from the
source to pass through – particularly if
it is dominated by a single line