In 1888 Holden's correspondence with the USC&GS paid off when the transits were employed as part of the first Transcontinental Triangulation. These were located some 1400 feet east of Observatory Peak at the current site of the Carnegie double astrograph, but their eccentricity to the Fauth was surveyed. Though the declination transit was determined to be faulty during the observations the latitude value it produced is consistent with values at Observatory Peak to better than an arcsecond. The result from the longitude transit differs by a larger amount -- this is consistent with the accuracy of portable chronometers of that era and with the lack of knowledge of variations in earth rotation. Consequently these observations do not contribute much to this investigation.
Indications are that the Meridian Circle adopted responsibility for all transit observations before the turn of the century. Tucker engaged in 30 years of transit observations which gave a very precise astronomical latitude, but one which depends on the coordinate system of the Auwers catalog.
Lick participated in two international campaigns for the determination of longitude in 1926 and in 1933. For consistency with the other sites these were performed using a Bamberg transit setup just northeast of the Meridian Circle. The reductions of the second campaign were delayed until after seasonal variations in earth rotation were measured; these serve as the definitive measurements of the longitude of the Meridian Circle.
Tucker's published latitude of the Meridian Circle is unequivocally the best, but a systematic correction due to star catalogs must be applied to it. Because all of Tucker's original observations exist in published form it would be possible to determine a better value for the latitude using FK5 coordinates.
The longitude measurements were made before the advent of the Photoelectric Zenith Tube which has become the standard for all transit observations. BIH's published longitude of the Meridian Circle is unequivocally the best, but its validity depends on the understanding of earth rotation available in the 1930s. It is unlikely that any new reduction of the original data would produce a better result.
Transfer of these coordinates to other sites requires extrapolation across the gravity field of Mt. Hamilton. The NGS has a gravity model for the US, but it is tabulated on the geoid using a 3 arcminute grid. Even if it were not itself based on interpolations of sparser data such a grid is not sufficiently dense, and Mt. Hamilton is significantly above the geoid. The shape and height of Mt. Hamilton could easily contribute to deflections of the vertical in excess of 1 arcsecond due to curvature of the plumb line. Variations of the plumb line curvature as large as 1 arcsecond across the mountain itself cannot be excluded. In short, it is presumptive to quote sub-arcsecond astronomical positions for anything not on Observatory Peak.
Meridian_Circle +37:20:25.75 -121:38:44.115 Bamberg_Transit +37:20:26.1 -121:38:43.440 Fauth_Transit +37:20:25.83 -121:38:44.579
Small_Dome (Nickel) +37:20:26.02 -121:38:45.486 Lick_36 +37:20:23.79 -121:38:45.99 Astrograph +37:20:29.2 -121:38:28.1 Shane +37:20:30.8 -121:38:24.9
Mt_Ham_Ecc +37:20:26.07 -121:38:46.077