A secchi disk is a black and white coloured disk used to determine water clarity. The disk is lowered into the water. The point at which you can no longer distinguish the black and white, is called the secchi depth.

(SECK-key) Disc - A flat, white disc lowered into the water by a rope until it is just barely visible. At this point, the depth of the disc from the water surface is the recorded seechi disc transparency.

a simple black and white disk used to measure water transparency or clarity.

Volcano on the surface of the moon mentioned by Julian 5th when The Barsoom passes close to the surface. Named after Angelo Secchi, Italian astronomer (1818-1878), a pioneer in identifying the volcanoes of the moon. [MMa

Secchi is a small lunar crater formation on the northwest edge of Mare Fecunditatis. To the northeast is the Taruntius crater. The western rim is joined with a section of the minor Montes Secchi range.