n (astronomy) A kind of
telescope mounted so as to have two
axis|axes of
motion at
right angles to each other, one of them
parallel to the axis of the
Earth, and each carrying a graduated circle, one for measuring
declination, and the other right
ascension, or the hour angle, so that the telescope may be directed, even in the
daytime, to any
star or other object whose right ascension and declination are known.