Kansas Academij of Science. 49 



OBSERVATIONS ON JUPITER AT THE OPPOSITION, 1915. 



Edison Tjottit. 



THE following observations on Jupiter were begun with 

 the Yerkes forty-inch telescope and completed with the 

 Washburn College twelve-inch telescope and position microm- 

 eter. The observations were made (1) to determine the 

 rotation period in various latitudes where markings of definite 

 character might be found; (2) to determine the polar com- 

 pression; (3) on the "great red spot"; (4) to measure the 

 diameters of satellites; (5) to determine the character of any 

 markings on the satellites. 



GENERAL FEATURES. 



From twenty-five observations, a map in Mercator projec- 

 tion was drawn. This takes system II of the Ephemeris as a- 

 basis of the longitudes. The quadrant from 180° to 270' was 

 not well observed. Since the planet was near equinoctial, ob- 

 servations were _ confined to positions near the meridian. 

 Powers of 750 and 1,000 were used on the forty-inch, and all 

 observations with the twelve-inch were made with a power of 

 1,000. Very clear weather during October and November 

 greatly focilitated observation. Especially clear weather was 

 taken advantage of to measure the satellites, which otherwise 

 flared too much. 



Almost all the surface features lie between the 30" parallels 

 of latitude. Plumelike markings were a quite prominent fea- 

 ture. A peculiar marking was observed on many nights in the 

 southern band, longitude 300° to 360°, latitude — 15° to — 30°, 

 like a grove of trees. Attention is especially called to two small 

 dark spots, the following one in longitude 309.8°, latitude 15° 

 north. This latter is especially adapted to the determination 

 of rotation period, being small and round and of considerable 

 depth of color. Its actual diameter is 2,100 miles, about that 

 of the moon. 



A faint line running around the planet in latitude 32' north 

 is widened to a short, thick band in longitude 85° to 105°. 

 This is also well adapted to the determination of the rotation 

 period. The white spots in the neighborhood of longitude 345'' 

 were brilliant and in general of a lemon shape. 



4— Sci. Acad.— 2163 



