A measure of the brightness or luminosity of a star or other celestial object.

The larger the number referring to the magnitude, the fainter the object.

Zero, or first magnitude, indicates some of the brightest stars.

Still brighter are those of negative magnitude; such as, Sirius, whose magnitude is -1.46.

1. The magnitude a celestial object would appear to have if it were at a distance of ten parsecs (10 times 3.261633 light years or 32.62 parsecs).
2. A measure of the true or intrinsic brightness of a star as if all stars were the same distance (32.6 light-years) from the observer.

The absolute magnitude of an object measured through a special yellowish filter that approximates the visual range of the human eye.

1. Magnitude as seen by an observer.
2. The brightness of a star as seen from the earth.
3. A measure of the brightness of stars as they appear on the celestial sphere.