Moment magnitude scale it is based on, is not measured routinely for smaller quakes. For example, the United States Geological Survey does not use this scale for earthquakes with a magnitude of less than 3.5, which includes the great majority of quakes. Current practice in official earthquake reports is to adopt moment magnitude as the preferred magnitude, i.e., is the official magnitude reported whenever it can be computed. Because seismic moment (, the quantity needed to compute ) is not measured if the earthquake is too small, the reported magnitude for earthquakes smaller than is often Richter's . Popular press reports most often
Absolute magnitude and a difference of n magnitudes in absolute magnitude corresponds to a luminosity ratio of 100. For example, a star of absolute magnitude M=3 would be 100 times more luminous than a star of absolute magnitude M=8 as measured in the V filter band. The Sun has absolute magnitude M=+4.83. Highly luminous objects can have negative absolute magnitudes: for example, the Milky Way galaxy has an absolute B magnitude of about −20.8. An object's absolute bolometric magnitude represents its total luminosity over all wavelengths, rather than in a single filter band, as expressed on a logarithmic magnitude scale. To convert