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A&A Supplement Series, Vol. 125, November I 1997, 595-603

Received September 24, 1996; accepted January 31, 1997

New methods of forming and aligning the instrumental frames of absolute transit circle catalogs

E.R. Holdenried and T.J. Rafferty

Send offprint request: E.R. Holdenried
United States Naval Observatory 3450 Massachusetts Ave. NW Washington DC, 20392-5420, U.S.A.


A new method of defining the declination axis of the instrumental frame of an absolute transit circle catalog has been developed utilizing observations from stars over the entire sky rather than, as in the past, observations of just circumpolar stars. This method allows the planetary observations to be used directly to align the axes of the instrumental frame thus constructed with DE200. The alignment process has been simplified and recast so that it does not feed back into the definition of the instrumental frame. A declination offset, which is unique to absolute transit circle observational catalogs, is discussed emphasizing the problem of its cross-correlation with rotation terms from the alignment process. When compared to "traditional" methods, these new procedures give similar results for those quantities in common but they also produce additional adjustments that were not accounted for previously.

keywords: astrometry -- methods: data analysis -- instrumentation: miscellaneous

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