The remedy proposed by Repsold for this proved fault is to cause the whole slide to tilt instead of the microscope only; this should prove a complete remedy.
2940, Dr Repsold proposed a method of meridian observing which consists in causing a web to follow the image of a star in transit by motions communicated by the observer's hands alone, whilst electrical contacts on the drum of the micrometer screw register on the chronograph the instants corresponding to known intervals from the line of collimation.
3377, Repsold gives a detailed description of two forms of eye-ends of transit circles, fitted with means of observing in this manner, to which he gives the name of " the impersonal micrometer."
In the case of the original Repsold plan without clockwork the description is not quite exact, because both the process of following the object and correcting the aim are simultaneously performed; whilst, if the clockwork runs uniformly and the friction-disk is set to the proper distance from the apex of the cone, the star will appear almost perfectly at rest, and the observer has only to apply delicate corrections by differential gear - a condition which is exactly analogous to that of training a modern gun-sight upon a fixed object.
It differed only from the three Russian instruments in having a mounting by the Cookes in which the declination circle reads from the eye-end.5 This instrument was afterwards most generously lent by Lord Lindsay to Gill for his expedition to Ascension in 1877.6 These four Repsold heliometers proved to be excellent instruments, 5 For a detailed description of this instrument see Dunecht Publications, vol.
Repsold heliometer (fig.
REPSOLD, JOHANN GEORG (1771-1830), German instrument maker, was born at Wremen in Hanover on the 23rd of September 1771, and became an engineer and afterwards chief of the fire brigade in Hamburg, where he started business as an instrument maker early in the 19th century.
Repsold introduced essential improvements in the meridian circles by substituting microscopes (on Jesse Ramsden's plan) for the verniers to read the circles, and by making the various parts perfectly symmetrical.
But after the discontinuance of this firm that of Repsold again came to the front, not only in the construction of transit circles, but also of equatorial mountings and more especially of heliometers (see Micrometer) .
For the great refractor more recently erected at Potsdam, Messrs Repsold arranged a large platform mounted on a framework which is moved in azimuth by the dome, so that the observer on the platform is always opposite the dome-opening.