Explanation of the Equatorial I & II tables:

An equatorial table, also known as an equatorial platform or equatorial mounting, is a device used to align and track celestial objects in the night sky. It consists of a platform or mounting that can be adjusted to match the Earth’s rotational axis. This alignment allows telescopes or other observational instruments mounted on the platform to follow the apparent motion of celestial objects as the Earth rotates, compensating for the Earth’s rotation and keeping the object within the field of view.

Equatorial tables are essential for astronomical observations, particularly for long-exposure astrophotography or detailed visual observations of celestial objects. They provide a stable and precise means of tracking celestial targets, enabling astronomers to study stars, planets, galaxies, and other astronomical phenomena with accuracy over extended periods of time.

The following was translated from an old German Book:

Explanation of the Equatorial I & II tables:

Both objectives are closed by roller shutters that can be opened from the eyepiece end. The facilities for clamping and moving the telescope in altitude and declination, as well as the reading microscopes, are also located there. The weight of the movable parts of the instrument is 7000 kg. The dome, with a diameter of 22 m and a height of 18 m, which covers the instrument, is made of iron and is supported by 20 triple images, with the middle one supporting the dome while the others run on a circular track resting on the masonry. The weight of the dome is 200,000 kg, and it can be rotated by a handwheel or an electric motor. The slit of the dome has a width of 3.5 m and extends 1.5 m above the zenith. The sliding shutter that covers it is operated manually from a gallery inside the dome wall or electrically from the observation chair.

The observation chair has a completely new design; it is not completely free to move like the equatorial mount of the observatory in Nice. Instead, it is fixed opposite the slit opening in the dome. As a result, when the dome rotates, the chair moves along with it, allowing the observer to always maintain their position relative to the slit. However, the chair can still be moved to the right and left within certain limits. The platform on which the observer is located moves up and down on an inclined plane. All of these movements can be performed manually or with the help of electric power. The necessary circuits and electrical measuring instruments are arranged on the platform of the observation chair, allowing the observer to control and regulate all movements of the dome, slit, and observation chair from there.

To avoid the inconveniences associated with the movement of a conventional equatorial mount, Loewy proposed the use of a right-angled broken telescope in 1871. Figure 8 shows a schematic representation of such a broken *Equatorial conde (Elbow Equatorial) at the observatory in Nice. The polar axis, supported by two pillars, is hollow and carries the eyepiece at its upper end. At its lower cubical extension, the shorter tube carrying the objective is attached at a right angle to the polar axis and can rotate around it. Inside the cube, at a 45-degree angle to the axes of the two telescope halves, there is a silvered glass mirror that reflects the light rays coming from the objective to the eyepiece. Since this mirror remains in the same position, the observer does not need to change their position even when the polar axis is rotated. Another mirror, inclined at 45 degrees to the optical axis, is placed in front of the objective and can rotate around its axis. When this mirror is rotated, it reflects into the telescope the light of stars from a certain circle of declination that is perpendicular to the optical axis of the objective half of the telescope, thus indicating the change in declination. This mirror is therefore connected to the declination circle, which, along with the hour circle, is located at the eyepiece end of the polar axis. The handles for clamping and fine movement of the telescope and the additional mirror are also located there. Thus, the observer can move and adjust the instrument in any direction without leaving their position at the eyepiece end, allowing for observations under the most favorable conditions and in a comfortable manner, even in a heated room, as only the eyepiece end is inside it, while the objective and other parts are outside and protected from the elements by a movable shelter that is pushed aside during observation.

Equatorial Platform 

A similar equatorial to the Equatorial conde has been constructed by Grubb and installed at the observatory in Cambridge, England (Fig.4). The polar axis is also supported by two pillars. At its lower end, it carries the declination axis, and on this axis, a shorter tube carrying the objective rotates. Concentric with the declination axis, there is a second axis that carries a plane mirror, which is always guided in such a way that it is hit by the light rays that enter the objective from a star and is reflected in the direction of the polar axis, creating an image at the focal point at the upper end of the polar axis. Therefore, the observer always remains in the same position and looks from above to below, just like with the Equatorial conde, in the direction of the polar axis. The main difference from the Equatorial conde is that this instrument uses only one mirror.

Equatorial Platform 

Fig. 1 of the panel shows the large 30-inch refractor of the Russian main observatory in Pulkovo near St. Petersburg, whose objective lens, made by Alvan Clark in Cambridgeport (United States), has a clear aperture of 762 mm and a focal length of 14.12 m. The mounting of the instrument is executed in the usual German configuration by Repsold in Hamburg. Resting on a sturdy, hollow column of cast iron, standing on a large cone below the floor on the foundation, is the bearing bushing of the polar axis made of cast steel, which carries the hour circle at the upper end. Perpendicular to the polar axis stands the declination axis also made of cast steel, which at one end carries the telescope and close by the declination circle, and at the other tapered end carries the counterweights balancing the weight of the telescope. The pressure exerted on the bearings of the polar axis by the entire weight of the instrument is counteracted by a heavy counterweight suspended on a chain inside the cast-iron column extending down to the foundation. Hence, the axes of the instrument lie with very little pressure in their bearings, allowing for very smooth movement of the entire instrument.

The telescope consists of a common central piece and two steel tube sections, the objective tube and the eyepiece tube, which have closable openings at both ends for ventilation of the tube. At the eyepiece end, there is a plate for holding a facula micrometer with position circles (see micrometer) and various auxiliary apparatus, including an electric dial connected to a sidereal clock, providing the observer with the current sidereal time. Parallel to the main telescope, at the eyepiece end, there is also a second, smaller telescope of 16 cm aperture, the finder, with low magnification and a wide field of view, so arranged that the center of the field of view of the finder corresponds to the field of view of the main telescope; the finder is used to locate objects whose position is only approximately known. To adjust the telescope to an object of known hour angle and declination without directly reading the circles, which would be difficult given the large dimensions of the instrument, two long microscopes are placed parallel to the telescope and firmly connected to it; these microscopes, by means of prisms, project an image of the divisions of the search circles to the eyepiece end of the telescope, allowing the observer to read the circles from his position. Furthermore, the telescope can also be adjusted from the platform erected on the column, where an assistant usually sits during observation, as the lower end of the polar axis also carries a hour circle easily readable from there and a second declination circle, which is mounted inside the declination axis and can be read by means of a microscope with a prism; the rotation of the instrument around its two axes can be easily executed from there by handwheels. To prevent rotation of the telescope about one of its axes or both simultaneously after adjustment, the same can be clamped by two keys located next to the telescope at the eyepiece end, and after clamping, still, by two other keys also located at the eyepiece end, a small rotation of the telescope around each of its two axes can be imparted, as is necessary for fine adjustment of an object.

Equatorial Platform 

The illumination of the instrument is provided by a petroleum lamp, which illuminates all circles of the instrument by means of various mirrors and prisms and produces field and thread illumination for the micrometer. To track the motion of the stars with the telescope, a clockwork with a heavy pendulum regulator is placed on the wall of the observation room, which, by means of various gears and connecting rods below the floor and inside the column, as well as by means of a worm screw, acts on a toothed circle located next to the hour circle on the polar axis and produces a rotation of the telescope around the polar axis once in a sidereal day. To provide the observer with a convenient position in front of the eyepiece in all positions of the telescope, two elevators on rails are movable around the instrument, one of which runs on a high gallery; each of these elevators contains a seat, which the observer can easily raise and lower without leaving his position by means of a simple winch, as well as move the seat on the rails by means of hand ropes. In recent times, in order to dispense with the elevators, which always require a lot of space, the floor of the entire observation room has been made not firmly connected to the building structure but arranged in such a way that it can be easily raised or lowered to any desired height by means of hydraulic presses, so that the eyepiece end of the telescope is always easily accessible without any ladder or elevator. This arrangement is carried out at the Lick Observatory and the Yerkes Observatory.

Equatorial Platform

The tower covering the Pulkovo refractor does not have the usual form of a dome (cf. observatory), but has vertical walls with a slightly inclined roof, which has an opening that can be closed by flaps; the entire tower rests on 10 wheels on the massive substructure and can be rotated by applying electric power to it. The height of the entire observation hall from the tower gable to the ground is 22 m. The instrument was installed in 1884 and was then the largest refractor in the world, but now ranks sixth. In Germany, the largest telescope is the double refractor of the Astrophysical Observatory in Potsdam (Fig. 2), which was completed in 1899. The mounting of this instrument, made by Repsold in Hamburg, is very similar to that of the Pulkovo refractor, except that, as it is mainly used for astrophysical work, it is equipped with two separate telescopes, enclosed by a common jacket of sheet steel. Of the two objectives, made by Steinheil in Munich, the larger one has an aperture of 80 cm and a focal length of 12 m and is achromatized for the chemically active rays; either a photographic cassette or a spectrograph can be attached to this telescope (cf. Astrophysics panel). The smaller objective has an aperture of 50 cm and a focal length of 12.5 mm, and it is also achromatized for the optical rays; at the eyepiece end of this telescope, there is a position micrometer.