200 



CARNEGIE INSTITUTION OF WASHINGTON. 



N.G.C. 



2274-5 

 2288 

 2359 

 2964 



Very faint, with relatively bright nuclei. 



Several small faint spirals including N. G. C. 2888-91, 2894. 



Gaseous, irregular. Lies in Milky Way. 



Right-handed spiral, 2968 same, 2970 nebulous spot. 



Nova Persei Nebulous ring just seen on 10-minute exposure. 



JUPITER'S NINTH SATELLITE. 



An ephemeris of Jupiter's ninth satellite was computed by Mr. 

 Nicholson for the 1917 opposition. The satellite was found near the 

 computed place on two negatives taken by Mr. Shapley with the 

 60-inch reflector. The positions were measured on these plates. 

 The orbit is being carried forward by the method of special perturba- 

 tions. 



MEASUREMENTS OF PARALLAXES AND PROPER MOTIONS. 



At the 80-foot focus of the 60-inch reflector 320 photographs with 

 447 exposures were secured by Mr. van Maanen as follows: 



The measures and reductions were completed for 26 fields, thus 

 giving a total of 80 finished fields. While most of the objects were 

 stars with proper motions less than 0T5 annually, of magnitude 5 

 to 7 and of later spectral types, the following nebulae and peculiar 

 stars were also included: 



Parallaxes have now been determined here for three planetary 

 nebula, viz, N. G. C. 2392, 6720, and 7662; including the value given 

 by Newkirk for N. G. C. 6720, we derive the following absolute 

 magnitudes of their central stars: +6.1, +8.1, and +9.4, respectively, 

 or, in the mean, +7.9. This result is strikingly close to the mean 

 absolute magnitude, +6.9, found for the three novse at minimum, 

 for which parallax determinations are available. In both cases we 

 seemingly have bright-line stars of faint absolute magnitude, while 

 ordinary stars of type have very high luminosities. 



