Deflection of the Graduator in the LLMC

The phenomenon of the divided circle deflection in the LLMC is narrated in this paper.The effect of the deflection on the measured values of the scales with the Reticon in the reading microscope systems is described.The reasons that make the circle deflection are analyzed,and a modification method is presented.It is discussed that whether or not the scales need to be added for a correction term related to zenith.it is concluded that the term need not to be added if the off-center of the circle is controlled within 5μm.