Absolute magnitude from an absolute magnitude in a specific filter band to absolute bolometric magnitude, a bolometric correction is applied. For Solar System bodies that shine in reflected light, a different definition of absolute magnitude (H) is used, based on a standard reference distance of one astronomical unit. In stellar and galactic astronomy, the standard distance is 10 parsecs (about 32.616 light-years, 308.57 petameters or 308.57 trillion kilometres). A star at 10 parsecs has a parallax of 0.1″ (100 milliarcseconds). Galaxies (and other extended objects) are much larger than 10 parsecs, their light is radiated over an extended patch of sky, and
Light and air unit Light and air unit A light and air unit, also known as a breathing support unit, is a specialized piece of firefighting apparatus used by firefighters to provide supplemental lighting and SCBA air bottles at the scene of an emergency. During prolonged emergencies, particularly structure fires, where firefighters must remain on air (wearing their SCBAs), these air bottles will need to be replaced and refilled. The light and air unit has the ability to refill the SCBA bottles while in the field using onboard air compressors. It also carries a supply of spare air cylinders. These units are highly customizable