In order to be suitable for such precision measurements, the optical and mechanical design of the eyepiece must allow the appropriate measuring unit to be attached to its focal plane . The micrometer replaces the usual cross-hairs or reticules . The first measuring eyepieces were constructed as early as the 17th century and further developed by astronomers such as Wilhelm Herschel or Friedrich Wilhelm Bessel , primarily for geographic location determination and for measuring star coordinates and double stars . They reached their technical perfection in the 19th century - among others by the companies Repsold and Starke & Kammerer - or (for special purposes) in the early 20th century. Finally, new types of micrometers and targeting methods were also stimulated by space travel and satellite geodesy .
The most important classical construction methods include the filament micrometer , the ring micrometer and the recording micrometer (impersonal micrometer) most commonly used in geodesy for the semi-automatic time determination with celestial bodies. With universal instruments (e.g. the DKM3 ) it can be rotated by 90 ° and thus also used for precise width determination according to Horrebow-Talcott .