Equatorial sextant

One historically significant instrument called by that name was John Flamsteed's equatorial sextant, installed in the Greenwich Observatory in 1676.

Seven feet across and possessing an iron frame,[1] it was mounted at an angle that aligned with the celestial equator, so that as it rotated, it tracked the motion of objects across the night sky.

[2] Flamsteed used this instrument to measure angles of right ascension from 1676 through 1689[3] or 1690.

[4] Another device known by that name was patented by the American inventor William Austin Burt in 1856.

[5] Burt's equatorial sextant included several elaborations on the basic sextant design, which enabled its user to determine navigational information without a supplemental chart or the need for calculation.