Investigation of Diameter Corrections of the Brorfelde Transit Circle

At the transit circle in Brorfelde a comparison has been made between several determinations of diameter corrections of which the latest has been performed with automatic telescope setting and circle reading. The difference between new and old diameters is around 0".09. No significant systematic changes in the diameters were found, although the division line engravings were refilled in 1973. The internal mean error of one diameter correction is 0".035. Using six diameters in observing a star, the remaining systematic error arising from errors in the diameter corrections, rarely exceeds 0".1 in declination.

The circle reading micrometers have been improved with stepping motors so that the use of reference lines can be avoided.