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
USS PC-823 York, ROKN’s first ocean-going naval vessel, Baek-du-san (PC-701) was born. Sailing from New York, a 3-inch main deck gun was attached at the Hawaii Naval Station, and 100 shells were purchased at Guam. PC-701 finally arrived at Jinhae Naval Base, South Korea, on 10 April 1950, barely two months before the June 1950 outbreak of the Korean War. With only 100 rounds ammunition, the sailors could only practice aiming the main gun, not firing it. On the night of 25/26 June 1950, on the South Korean eastern coast, she patrolled against infiltrators from the north. About twenty miles from the