Aim failure
In astrometry and geodesy, the aiming error is the small angular error by which the sighting axis of a telescope , which was aligned by the observer or the measuring sensor, deviates from the image of the object to be measured .
extent
With a good theodolite the aiming error - depending on the experience of the observer - amounts to around 1 ″ (0.0003 °), with a large astronomical meridian circle about 0.1 ″ and with the astrometry satellite Hipparcos about 0.01 ″.
Shares
Every target error consists of a random component - which can be reduced to the most plausible value by adjustment - and a systematic error that depends on the observer, the measuring instrument and the external conditions (weather, etc.). Its reduction is much more difficult and depends on the appropriate modeling and physical correlations .