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Published online by Cambridge University Press: 12 April 2016
Automated photoelectric meridian circles are able nowadays to have the full set of graduation errors of the decimation circle determined within a few days. Thus, the modern meridian circles can be monitored, and the annual and secular changes of the graduations can be easily detected to provide the graduation corrections at any date. In order to remove systematic declination errors in the form Δδα from absolute catalogs, these continuous changes should be taken into account.