Quote:
Originally Posted by Shipwreck
1. Unlike Turrets II & III, Turret I had a Mark-53 coincidence rangefinder.
2. This Mark-53 coincidence rangefinder was removed on all four Iowas in the 1950s.
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Correct.
As built, all three turrets on the Iowa class had 25 power, 46 foot (14 m) rangefinders, with Stereoscopic Mark 52 used in Turrets II and III and Coincidence Mark 53 in Turret I. The Mark 52 weighs 10,500 lbs. (4,763 kg) and cost about $100,000 US during World War II. Near focus for the Mark 52 is 5,000 yards (4,570 m) and the maximum range is 45,000 yards (41,150 m). Mark 53 was a coincidence type with a special astigmatic lens which allowed it to range in on a single point source, such as a searchlight. In the 1950s, the Mark 53 rangefinder was removed as weight compensation for growth in other areas. This rangefinder was selected as the increasing sophistication of fire control radar made its special capability redundant. The lower height of Turret I above the water also meant that this mounting had a shorter distance to the horizon capability. The openings in Turret I were then armor-plated over.