The first observer to catalog differences in star brightnesses was Greek astronomer Hipparchus. He created a catalog around 135 B.C.E. of roughly 850 stars divided into six ranges. He called the ...

There are a number of ways to measure the magnitude of an earthquake. Most scales are based on the amplitude of seismic waves recorded on seismometers. These scales account for the distance between ...

I.—APPARENT MAGNITUDES: (a) VISUAL.THE magnitude of a star, as determined by direct astronomical observation, is a measure of its apparent brightness on a scale which has been precisely defined only ...

where A is the maximum amplitude of deflection of a needle on a chart, in millimeters, measured on the seismograph. A o is an empirical distance correction appropriate for the region (Richter, 1936).

What is the baseline for determining the magnitude scale of celestial objects? Why do brighter objects have negative numbers? Dean Treadway Knoxville, Tennessee The first observer to catalog ...

II.—APPARENT MAGNITUDES: (b) PHOTOGRAPHIC. WITH the application of photography to astronomy it was inevitable that attempts should be made to determine apparent magnitudes by photography. Visual ...