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"Dollond's divided object-glass heliometer of the third type. A is the end of the reflecting telescope, upon which the adapter B is fitted. B carries a wheel (not seen in the figure) formed of a ring racked at the outer edge, and fixed to the brass plate CC, so that the pinion moved by the handle D may turn it into any position. Two plates F, G, with the attached semi-lenses, move in slides fixed to the plate CC, —simultaneous motion, in contrary directions, being communicated to them by turning the handle E, which drives a concealed pinion that works in the two racks seen in the highest part of the figure." —The Encyclopedia Britannica, 1903

Heliometer

"Dollond's divided object-glass heliometer of the third type. A is the end of the reflecting telescope,…

"No part of the equatorial mounting is shown in the figure, as it resembles every respect that usual Fraunhofer mounting. An adapted h is fixed on a telescope-tube, made of wood, in Fraunhofer's usual fashion. To this adapter is attached a flat circular flange h. The slides carrying the segments of the divided object-glass are mounted on a plate, which is fitted and ground to rotate smoothly on the flange h. Rotation is communicated by a pinion, turned by the handle c, which works in teeth cut on the edge of the flange h. The counterpoise w balances the head about its axis of rotation. The slides are moved by the screws a and b the divided heads of which serve to measure the separation of the segments. These screws are turned from the eye-end by bevelled wheels and pinions, the latter connected with the handles a', b'." —The Encyclopedia Britannica, 1903

Heliometer

"No part of the equatorial mounting is shown in the figure, as it resembles every respect that usual…

"The type of instrument which resulted from Russian labors. The brass tube, strengthened at the bearing points by a strong truly-turned collars, rotates in the cast-iron cradle g attached to the declination axis. a is the eye-piece fixed in that axis, b the micrometer for reading both scales." —The Encyclopedia Britannica, 1903

Heliometer

"The type of instrument which resulted from Russian labors. The brass tube, strengthened at the bearing…