Flux Density Spectral Energy Density

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

Photmetric Magnitudes Filters Johnson UBV Bands Zero Point Set using Vega

Apparent Magnitude Zero point? Magnitude difference of 5

Absoulte Magnitude Intrinsic Property of the Source – Luminosity

K correction Distance Modulus

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