Secchi Disk(redirected from Secchi disk transparency)
Also found in: Dictionary.
Secchi disk[′sek·ē ‚disk]
an instrument for measuring water transparency in a body of water. A white disk 30 cm in diameter, it is held horizontally and lowered into the water on a rope until it is no longer visible. The depth, in meters, at which it ceases to be visible is taken as a measure of the water transparency. The disk is named after A. Secchi, who measured the transparency of sea water by this method in 1865.