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

Abstract

A new method of dening the declination axis of the instrumental frame of an absolute transit circle cat- alog 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 plane- tary observations to be used directly to align the axes of the instrumental frame thus constructed with DE200. The alignment process has been simplied and recast so that it does not feed back into the denition of the in- strumental frame. A declination oset, which is unique to absolute transit circle observational catalogs, is discussed emphasizing the problem of its cross-correlation with ro- tation terms from the alignment process. When compared to \traditional methods, these new procedures give sim- ilar results for those quantities in common but they also produce additional adjustments that were not accounted for previously.