FOR THE EPOCH 1910
BY ARTHUR J. ROY
The observing list for this catalogue, as decided upon bycorrespondence between Professor George C. Comstock and Dr. Lewis Boss, was made up of the stars in the Albany observing list between +30δ and -21δ 30δ,and in the next magnitude fainter than those in the Preliminary General Catalogue.With few exceptions, the magnitudes ranged from 5.8 to 7.0 and were well observable with the Washburn meridian circle. In the cooperative arrangement it was planned that two observations of each star would be taken at Albany and two at Madison. As it turned out, the present catalogue contains positions of 2403 relative stars and of 383 standard stars.
The instrument used was the Repsold meridian circle of 12.2 cm aperture equipped with the transit micrometer driven by hand and rotating slat screens with which the standard stars were reduced approximately to the brightness of the relative stars. A full description is given in volume 12 of the Publications of the Washburn Observatory. The same values of the micrometers were used,namely 6.s2923 in right ascension and 94″348 in declination. The value of the right ascension micrometer was tested by taking the differences between the two halves of forty transits of close equatorial stars observed on August 23,August 27, and September 8, 1916. The value found, 6.s288, differed so little from the adopted value that it was deemed inadvisable to make any change in the reductions, or to investigate further.
The method of reduction differed in some respects from the previous practice. As mentioned elsewhere, the use of circumpolar stars to determine n was abandoned and it was determined from pairs of time stars differing widely in declination. The solutions for the clock rates and the change of the equator points (with a few exceptions) were made by least squares instead of by graphs.
The positions of the standard stars are those of the General Catalogue but were taken from the papers of the Dudley Observatory before publication of that catalogue. The Madison positions of the standard stars are given in the present catalogue only when the number of standards in a series exceeded seven, as with small numbers there was too much tendency to reproduce the standard position.
When this series of observations was begun, the use of the transit micrometer had not wholly emerged from the experimental stage. The triple signal opposite the zero of the micrometer head, mentioned on page 1000*** 242 of volume 12, greatly