With the instrument regulated in this way it is sufficient to rotate the alidade with respect to its two orthogonal axes so that the lens it is equipped with forms the image of the sun on the screen opposite it projected on the etched circle.
At that point the alidade will be inclined on the plane of the circular quadrant (the equatorial plane) by an angle equal to the declination of the sun at the time of observation, while the end of the rod holding the alidade will show on the circular quadrant the hourly angle of the sun expressed in hours and minutes, which is to say so-called apparent solar time. By applying to the latter a double correction equal to the local longitude with respect to the central meridian of the time zone and the time equation, we obtain the mean solar time.
The vicissitudes of the builders Georg Friedrich Brander (1713-1783) and Cristoph Caspar Höschel (1744-1820) lead us to believe that the instrument was built prior to 1873 or just a few years after that date.
Indeed, Brander, in order to meet the great and ever-growing demand for his instruments owing to their accuracy and precision, expanded his shop in Augsberg and brought his son-in-law Höschel into the business in 1760. Starting in 1775 the trademark became: Brander e Höschel in Augsburg.
With Brander's death in 1783, Höschel became the sole owner of the shop; at a certain point the trademark began appearing as Höschel and, from 1820, Höschel and Son.