A device used e.g. on a rifle in aiming a projectile, through which the person aiming looks at the intended target.

plural of Galilean telescope

plural of Dobsonian telescope

(astronomy) A type of reflecting telescope employing a parabolic liquid mirror made by spinning a pool of reflective liquid.

(astronomy) An instrument that detects X-rays originating from outside the Earth's atmosphere.

plural of liquid mirror telescope

plural of X-ray telescope

(figuratively) With the opposite of what is the correct conclusion.