Mural instrument

Edmond Halley, due to the lack of an assistant and only one vertical wire in his transit, confined himself to the use of a mural quadrant built by George Graham after its erection in 1725 at the Royal Observatory, Greenwich.

More recent instruments were made with a frame that was constructed with precision and mounted permanently on the wall.

[2] In order to measure the position of, for example, a star, the observer needs a sidereal clock in addition to the mural instrument.

With the clock measuring time, a star of interest is observed with the instrument until it crosses an indicator showing that it is transiting the meridian.

If the instrument's arc is not marked relative to the celestial equator, then the elevation is corrected for the difference, resulting in the star's declination.

Tycho Brahe 's mural quadrant
Mural quadrant constructed as a frame mounted on a wall. This instrument was made by John Bird in 1773 and is in the Museum of the History of Science, Oxford .
A Bird Mural Quadrant was for many years the main instrument of the Mannheim Observatory in Germany, shown here installed.
Ulugh Beg 's mural sextant, constructed in Samarkand , Uzbekistan, during the 15th century