EXCHANGE *UG 20I9IJ Determination of the Mean Declinations of 136 Stars FOR THE EPOCH 1912.0 A THESIS PRESENTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF PENNSYLVANIA BY WILLIAM ELIJAH ANDERSON IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY PHILADELPHIA 1913 PHILADELPHIA THE JOHN C. WINSTON CO. 1913 Determination of the Mean Declinations of 136 Stars FOR THE EPOCH 1912.0 A THESIS PRESENTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF PENNSYLVANIA BY WILLIAM ELIJAH ANDERSON IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY PHILADELPHIA 1913 PHILADELPHIA THE JOHN C. WINSTON CO. 1913 INTRODUCTION. The Wharton Reflex Zenith Tube of the Flower Observa- tory is an instrument of somewhat unusual design, but one capable of high accuracy in the measurement of the declina- tions of stars. Its precision for this purpose arises from the fact that no level readings enter into the observations, and hence the troublesome and uncertain variations which are found even in the most accurately constructed level tubes cannot with this instrument produce their usual anomalous effects. The excellence of this particular instrument for this special kind of work has been fully demonstrated by the extensive series of observations made with it by Pro- fessor C. L. Doolittle in connection with his researches into the variation of terrestrial latitude. As the field of this instrument extends to but little farther than 15' from the zenith, only those stars can be observed withit whose declinations are at this time nearly equal to the present latitude of the Flower Observatory. But as the diam- eter of the objective is eight inches, all stars so bright as those of the 8.5 magnitude can be well observed, and it was believed that the accurate determination of a narrow zone of these stars would be a work of value. The present thesis contains the results of a part of this work, the mean declinations of 136 of these stars, reduced to the epoch 1912.0, being here included. It is hoped that it will be possible to continue these observations until the entire zone has been twice passed over, and afterward to carry on systematic observations for parallax upon such of them as give evidence of a considerable proper motion. If this program is completed, the detailed figures of the obser- vations will be hereafter published as one of the volumes of the Astronomical Series of The University of Pennsylvania. Some six hours of every clear night are being at present devoted to this work, but a brief description of the method (3) of observation and a statement of the mean results thus far obtained seem all that it is necessary to publish at this time, while the zone is still incomplete. THE INSTRUMENT AND THE METHOD OF MAKING THE OBSERVATIONS. The following results were obtained from observations of a portion of a zone of stars lying within 15' of the zenith of the Flower Observatory of the University of Pennsylvania. The Observations were made with the Wharton Reflex Zenith Tube. This consists of an objective of eight inches aperture supported on a vertical tube, withiri which there is a basin of mercury at a distance of one-half the focal length below the center of the objective. The focus of the objec- tive is thus in the plane of the micrometer threads, 0.155 inches above the surface of the objective itself. By means of a diagonal reflector, the rays are next directed into one of two horizontal telescopes which rest upon the top of the tube and face east and west. The reticle contains two groups of three threads each which are placed parallel to the meridian, and a single, movable thread at right angles to these with which the decli- nations are measured. A star entering the field crosses the second thread of the first group about thirty seconds before the time of meridian passage and reaches the third thread after an interval of about eight seconds. A bisection of the star's image is carefully made with the movable transverse thread at the instant of its transit of each of these threads. The micrometer box, together with the diagonal reflector, is then turned through an azimuth of 180 degrees and the star again observed as it crosses the same two threads on the opposite side of the meridian. The four readings thus obtained are recorded on the self-registering micrometer head. This method of observing has the advantage of eliminating entirely all errors of azimuth and collimination. It has also been found that the objective may be kept so nearly level that the effect of any level error is entirely inappreciable. The only correction that need be applied to the observed zenith distances is hence that due to the fact that the bisec- tions are made when the stars are at a short distance from the meridian. It is found that when a star is first observed through the east telescope this correction is 0".38 and that when it is first observed through the west one the correction is 0".48. In the former case the observation is said to be "Direct," and in the latter, "Reverse." The aim was to observe each star Direct and Reverse alternately. (A detailed description of the instrument may be found in the Publications of the University of Pennsylvania, Astro- nomical Series, Volume III, Part, 1.) THE MICROMETER. The value of one revolution of the micrometer screw was determined by turning the instrument 90 degrees in azimuth, so that the movable thread was parallel to the meridian, and observing the times of transit of a star as it passed horizontally across the field. The movable thread was first placed near that edge of the field at which the star would first appear, the micrometer head being set at an even reading, and the time of transit was recorded on the chronograph. The thread was then moved forward two revolutions, another transit was recorded, and this was repeated throughout the field, 26 transits being thus taken for each star. From the results of observations on 34 stars the value of one revolution was found to be, R = 41 ".5430 =fc ".003 When the final values of the declinations were obtained, it became evident that this value was considerably too small and accordingly its correction was determined by a least square adjustment based upon all measured zenith distances which exceeded two revolutions of the screw. The resulting correction was -{-0".075; when this is applied we obtain the following value of one revolution of the screw, and this was employed throughout the following computation : This latter value agrees well with the value (jR = 41".60), employed by Professor C. L. Doolittle in his series of latitude observations. THE OBSERVING LIST. It was found that all stars of the 8.5 magnitude or brighter which lie within 15 minutes of arc of the zenith could be readily observed. The declination of the zenith throughout the twenty-four hours of. right ascension was therefore first reduced to 1855.0, the epoch of Argelander's Durchmus- terung, and all stars fulfilling the above conditions were selected from this catalogue as an observing list. There were thus obtained 586 stars. The present list comprises that portion extending from 22 hours to 5 hours right ascension. It was afterward found that all of these stars were also included in the two Astronomische Gesellschaft Zones, Lund 34 42' to 40 10', and Bonn 39 50' to 50 10'. The A. G. positions of the selected stars were next reduced to the epoch 1912.0 by the usual formulas, and from these reduced positions the star constants* a', b f , c' and d' were computed. With the help of these, and using the values of the Day Numbers from the American Ephemeris and Nau- vical Almanac, the results of the observations on each night were also reduced to the epoch 1912.0. The results of obser- tation were then compared with the A. G. positions and from this comparison the values of the proper motions given in the following table were determined. These are therefore provisional proper motions only, depending on a comparison of the A. G. positions with the positions here obtained alone. For the purpose of determining the declinations from the observations, there was assumed for the latitude the mean value, 39 58' 2".l This is the mean result obtained by Professor C. L. Doo- little from observations extending over a period of fifteen years. THE FINAL RESULTS. The final results of the work are stated in the following tables. The first three columns contain the reference num- bers, the A. G. numbers, and the A. G. magnitudes respec- tively; the fourth column contains the epoch of the present observations, the fifth column contains the mean declina- tions as derived from the observations and the sixth column states the residuals determined by subtracting from these positions the reduced A. G. results. It is from these that the several proper motions are computed, and the results of this computation are given in the seventh column. The last column states the number of nights on which each star was observed. Star A. G. No. No. Mean A. G. Epoch Mag. 1912.0 Final Mean Observed for 1912.0 Observed A?G. 1 10568 7.7 0.80 2 10624 6.2 0.80 3 10668 8.0 0.81 4 10723 7.2 0.81 40 2 51.38 -0.21 -0.005 3 40 13 23.21 + 1.95 +0.050 6 40 6 35.26 -1.48 -0.038 7 40 9 44.96 -1.70 -0.044 7 5 10770 8.9 ,79 39 55 41 .26 -0 .53 -0.014 6 10803 7.0 0. 84 40 8 30 .55 -1. 03 -0.027 7 10818 6.8 0. 82 40 12 44 .68 + 2 .25 -4-0.058 8 10831 5.7 0. 84 39 45 56 .05 +0 ,54 +0.014 9 10905 7.7 ,81 40 3 .11 -2 .30 -0.059 10 10928 7". 8 .84 39 47 55 .16 + 1 .83 +0.047 11 10950 5.8 0.80 39 54 27 ,44 + 1 .29 +o .033 3 12 11131 8.2 0.81 39 57 23. 45 .45 -0. 012 8 13 11166 7.9 0.81 39 45 3. 35 -0 06 -0, 002 8 14 11188 6.9 0.81 39 54 24, ,85 -3 .65 -0. 094 8 15 11243 8.9 0.81 40 2 8. 81 -0. 13 -0. 003 8 16 11262 8.0 0.82 40 0. 21 2 04 -0. 053 6 Star No. A. G. No. A. G. Mag. Mean Epoch 1912.0 Final Mean Observed for 1912.0 Observed A. G. / n _|_ o / n " 17 11288 7. 4 0. 83 40 4 5 . 94 -2. 42 -0 .063 5 18 11294 8. 4 o. 82 39 49 37.96 +o. 89 +0 .023 4 19 11304 9. 0. 84 39 49 11.20 -1. 21 -0 .031 5 20 11347 7. 1 0. 82 39 42 39.53 -1. 61 -0 .041 10 21 11383 7. 7 0. 82 40 6 45.78 +0. 91 +0 ,024 9 22 11426 8. 4 0. 83 39 55 21.36 -1. 35 -0. 035 6 23 11448 6. 7 0. 81 x 39 55 42.90 -0. 74 -0. 019 6 24 11 8. 8 0. 85 40 6 5.93 -0. 79 -0. 020 4 25 17 7. 2 0. 86 40 17.18 1. 19 -0. 031 4 26 21 8. 7 0. 85 40 8 40.12 +1. 35 +0. 035 '4 27 30 8. 9 0. 83 40 5 14.01 -3. 86 -0. 099 3 28 36 7. 8 0. 87 39 54 32.83 -1. 85 -0. 048 5 29 58 8. 2 0.84 39 55 50.62 -0. 85 -0 ,022 5 30 113 8. 8 0. 84 40 12 25.97 -1. 31 -0 034 9 '31 150 8. ,4 0. 84 40 1 54.21 -0. 10 -0 003 9 32 215 8, ,5 0. 83 39 57 57.09 +0. 01 + 000 6 33 234 7, 5 0. 86 39 50 53.24 -0. 35 ,009 5 34 241 8 .7 0, 86 39 57 14.30 -0. 11 -0 .003 4 35 260 7 .5 0, ,84 39 43 12.50 -15. 02 -0 .387 5 36 270 7 ,3 0, ,85 40 12 25.27 -2. 84 -0 .073 5 37 280 8 .6 ,87 39 55 12.23 -1. 29 -0 .033 3 38 285 7 .9 ,88 39 57 8.94 -1. 31 -0 .034 3 39 286 8 .7 ,87 40 12 15.83 + 1. 50 + .031 4 40 287 6 .8 ,92 40 11 53.97 +0. 73 +0 .019 3 41 294 8 .5 .89 39 46 12.66 -2. 40 -0 .062 4 42 298 8 .8 .89 39 56 38.90 -1. 97 -0 .051 5 43 315 8 .9 .84 39 49 12.25 -0. 19 -0 .005 6 44 340 6 .9 o .87 39 45 56.25 -0. 06 -0 .002 8 45 365 8 .2 o .86 39 54 21.28 -0. 83 -0 .021 5 46 375 8 .7 .89 40 4 24.35 + 0. 31 + .008 5 46' 381 9 .0 .88 40 2 45.79 -2. 07 -0 .053 3 47 468 8 .6 1 .00 40 11 24.03 -2. 59 -0 .067 1 48 487 8 .6 1 .00 39 59 32.17 -3. 55 -0 .091 1 49 488 8 .9 .85 40 10 27.14 -3. 10 -0 .080 10 50 531 8 .2 .87 40 11 4.47 -0. 77 -0 .020 9 51 548 9 .0 .87 39 45 39.57 -1. 08 -0 .028 6 52 577 7 .7 .86 40 9 2.19 +0.47 + .012 10 Star No. A. G. No. A.G. Mag. Mean Epoch 1912.0 Final Mean Observed fcr 1912.0 Observed A. G. f/ n _j_ o / a a 53 602 8.3 0.87 39 51 17 .94 -1 .67 -0 .043 6 54 611 8.6 0.89 39 53 17 .58 + 1 .77 +0 .046 4 55 621 6.1 0.86 39 52 47 .09 + .06 + .002 6 56 646 8.4 0.85 39 44 41 .84 _2 .36 -0 .061 10 57 710 8.0 0.86 39 50 5 .26 -0 .50 -0 .013 5 58 736 5.1 0.86 40 7 54 .85 + .08 +0.003 4 59 752 6.8 0.85 39 55 59 .63 -1 .24 .032 7 60 802 8.6 0.87 40 1 42 .40 -0 .59 -0 .015 6 61 827 8.2 0.88 40 11 17 .27 -0 .99 -0 .026 5 62 836 8.3 0.85 39 44 15 .03 +0.03 + ,001 5 63 847 7.3 0.92 40 13 25 .40 +0 .15 + .004 4 64 848 8.2 0.89 39 51 13 .60 i .88 -0, 048 4 65 861 8.9 0.86 40 50 .92 .69 -0. 018 3 - 66 916 7.9 0.85 40 8 16 .26 + 2 .49 + 0. 064 8 67 980 8.6 0.85 40 10 43 .47 + .57 +0. 015 11 68 1016 8.3 0.86 40 6 20 .46 + 0, 65 + 0. 017 8 69 1043 7.9 0.86 39 50 36 .25 + 0.81 + 0. 021 5 70 1052 7.2 0.87 40 5 50 .26 -2. ,73 -0. 070 6 71 1102 7.6 0.85 40 8 33 ,48 -2. 42 -0. 060 5 72 1111 7.8 0.89 39 52 21 .50 -1. 70 -0. 044 7 73 1122 8.4 0.85 40 3 42 53 -0. 84 -0. 022 7 74 1215 7.4 0.89 39 46 38. 22 + 0. 20 +0. 005 7 75 1232 7.3 0.87 39 53 0. 73 -1. 05 -0. 027 7 76 1248 8.4 0.88 39 54 22. 82 -0. 92 -0. 024 7 71 1251 7.9 0.90 40 12 40. 92 1. 18 -0. 030 7 78 1265 7.1 0.91 39 49 13. 74 -1. 83 -0. 047 4 79 1330 9.0 0.89 39 53 30.08 +4. 89 + 0. 126 6 80 1339 5.5 0.91 39 49 19. 11 -5. 48 -0. 141 3 81 1346 7.6 0.90 39 53 9. 82 -1. 08 -0. 028 3 82 1422 8.0 0.88 40 6 48. 89 + 0. 63 +0. 016 7 83 1450 8.2 0.87 39 46 27. 72 -0. 22 -0. 006 9 84 1506 8.4 0.86 39 53 50. 22 -0. 63 -0. 016 6 85 1523 8.9 0.90 39 56 18. 59 -0. 93 -0. 024 6 10 ' Star No. A. G. No. A. G. Mag. Mean Epoch 1912.0 Final Mean Observed for 1912.0 Observed n _j_ / if if 86 1543 7.0 0.88 40 4 6. 87 +o. 02 + 0. 001 5 87 1551 8.0 0.88 40 55. 56 -0. 87 -0, 022 6 88 1572 6.9 0.87 39 56 56. 18 1. 74 -0, 045 8 89 1595 8.0 0.89 39 51 46, ,83 -0. 42 -0 ,011 6 90 1601 8.0 0.87 39 44 48, 79 + 0. 39 +0 010 5 91 1658 8.4 0.88 39 49 24 .59 -1. 30 -0 .033 4 92 1668 8.4 0.88 39 52 21 . 11 1. 74 -0 .045. 4 93 1669 7.0 0.91 39 47 25 .35 -1. 01 -0 .026 5 94 1690 7.1 0.87 40 9 35, 61 + 1. 30 + ,033 9 95 1740 8.3 0.87 39 51 9. 61 + 0. 11 + .003 5 96 1750 7.2 0.91 39 43 54, ,21 -1. 19 -0 031 7 97 1753 7.2 0.90 39 54 39, 10 +0. 18 + 005 5 98 1770 8.2 0.89 40 8 57 ,25 1. 53 -0, .039 5 99 1785 6.8 0.87 39 51 56, .90 -1. 38 -0 ,036 5 100 1793 7.3 0.90 39 52 52 .65 -0. 75 -0 ,019 6 101 1850 7.3 0.88 40 37 .21 +o. 37 +o .010 8 102 1874 7.0 0.88 39 47 56 .99 -0. 90 -0 .023 8 103 1934 7.2 0.88 39 48 7 .71 -1. 19 -0 .031 7 104 1973 8.5 0.92 39 59 38 69 -1. 50 -0 ,039 4 105 1978 7.6 0.92 40 6 6 ,55 +0. 76 +o .020 4 106 1979 8.8 0.91 39 51 18 56 -2. 03 -0 .052 5 107 2019 3.3 0.90 39 45 22 .72 -1. 50 -0 .039 7 108 2040 7.4 0.89 39 45 47 96 + 0. 49 + ,013 3 109 2047 8.4 0.92 39 57 10 .51 -0. 93 -0 .024 3 110 2054 7.0 0.92 39 50 51 93 -3. 06 -0 ,079 5 111 2062 7.3 0.92 39 44 30 ,38 -1. 70 -0 ,044 3 112 2098 7.7 0.90 40 3 42 ,74 -0. 16 -0 ,004 10 113 2127 7.5 0.90 39 55 50 ,34 ? 80 -0. ,098 8 114 2158 7.7 0.91 40 8 1 ,05 -0. 63 -0 016 5 115 2147 8.5 0.90 40 2 13, 76 -0. 62 -0, 016 5 116 2202 8.0 0.89 39 42 8, 21 1 . 63 -0, 042 7 117 2182 7.8 0.90 39 48 26 .70 -0. 94 -0 024 9 118 2244 8.3 0.91 40 6 2 ,08 -1. 89 -0 049 8 II Mean Final Mean Observed Star A. G. A. G. Epoch Observed No. No. Mag. 1912.0 for 1912.0 A. G. 119 2218 7.0 0.91 39 43 42 .10 -1 .64 -0. 042 8 120 2270 6.9 0.95 39 49 10 .27 1 86 -0. 048 4 121 2264 8.0 0.89 39 57 16 .52 1 ,21 -0. 031 3 122 2305 8.5 0.91 40 7 14 .15 -1 .57 -0. 040 6 123 2274 8.3 0.95 39 44 9 .94 -1 .95 -0. 050 3 124 2357 6.1 0.93 40 9 11 .41 -2 .19 -0. 056 4 125 2340 8.3 0.91 39 42 41 .00 -3 .19 -0 .082 7 126 2399 8.0 0.92 39 51 38 ,40 + 0, 08 +0 .002 4 127 2363 8.7 0.95 40 4 28 .15 -0 .29 -0 .007 4 128 2417 8.3 0.91 40 1 43 .85 2 46 -0 .063 2 129 2410 8.3 0.95 39 45 43 .53 -1. 56 -0 .040 4 130 2435 8.7 0.94 40 6 52 37 + 0. 63 +0 .016 3 131 2431 6.9 0.95 132 2459 7.8 0.94 133 2452 7.0 0.94 134 2486 8.4 0.94 135 2478 8.0 0.95 39 55 20.44 39 49 47.45 40 6 2.78 39 50 43.80 39 57 2. 19 -4.31 -1.52 + 0.20 -1.42 -1.16 -0.112 4 -0.039 3 +0.005 3 -0.036 3 -0.030 4 OTHER CATALOGUE POSITIONS. The various available star catalogues were next examined for observations of these stars, with the result that of eight- een of them it was found that positions had been determined elsewhere. The eighteen stars, together with the names of the catalogues in which they are to be found, and the several determinations of the proper motions are stated in the following table. The abbreviation G. C. S. here signifies, "A New Reduction of Groombridge Circumpolar Stars," The Royal Observatory, Greenwich, 1905. Number. Catalogue. Star Name or No. 4 G. C. S. Grom. 3803 12 Lacertag 8 B. A. C. 7975 Gr. 9 yr., 1872 .2135 Brad. 3002 G. C. S. Groom. 3856 Mag. 5.5 6.0 -0.035 -0.01 -0.02 + 0.018 12 ^umbei . Catalogue. Star Name or No. Mag. ft' 10 G. C. S. Groom, 3908 + 0.015 11 Gr. 10 yr., Glas. 3838 G. C. S. Grom. 3919 6.1 + 0.051 B. A. C. 7984 6.0 Gr. 9yr., 1872 6.0 + 0. 114 39 G. C. S. Grom. 131 -0.026 40 G. C. S. Grom. 133 -0.007 44 G. C. S. Grom. 162 + 0.043 45 G. C. S. Grom. 178 -0.027 52 G. C. S. Grom. 302 + 0.009 53 G. C. S. Grom. 308 -0.005 55 G. C. S. Grom. 313 -0.019 58 Porter, 4280 stars. 317 5.5 G. C. S. Grom. 372 -0.029 Gr. 10 yr., Glas. 236 -0.015 Gr. 7 yr., 1864 227 5.0 -0.209 Boss 369 5.0 -0.025 B. A. C. 502 -0.09 Gr. 9yr., 1872 154 5.0 -0.09 T Andromedae 59 G. S. C. Grom. 368 + 0.014 63 G. C. S. Grom. 400 +0.013 80 G. C. S. Grom. 542 -0.191 Gr. 10 yr., Glas. 401 5.0 -0. 179 Gr. 7 yr., 1864 353 5.0 -0.348 Porter, 2030 stars 180 5.5 -0.182 B. A. C. 821 5.5 -0. 160 Boss 610 5.1 -0.191 94 Gr. 10 yr., Glas. 492 W. B. *IIJ 157 6.8 2 369 B. G. C. 1633 107 Persei Gr. 10 yr., Glas. 610 3.0 -0.016 B. A. C. 1219 3.5 -0.030 Boss 910 2.9 -0.029 Gr. 12 yr., 1847 336 3.4 -0.030 Gr. 9 yr., 1872 361 3.5 -0.040 G. C. S. Groom. .765 -0.027 Porter, 2000 stars. 463 145 * Companion star preceding, in A. G. CONCLUSION. The results of the observations thus far made, clearly indicate a considerable proper motion in several of these stars. This is especially marked in numbers 14, 27, 35, 48, 49, 79, 80, 113, 125, and 131. The large value from five accordant observations of number 35 is especially notable. If these values are confirmed upon the repetition of the obser- vation of this zone, it appears that the list will furnish several stars upon which parallax observations can be undertaken with considerable prospect of success. Gay] M Syraci Anders on* |E' 5. at ion of mean declinations stars the A