MOUNT WILSON OBSERVATORY. 239 



N. G. C. 48, 49, 50. Group of 11 small nebulae, 9 elliptical, 2 irregularly round. 



N. G. C. 3786 and 3788. Right-handed spirals just touching; 27 additional nebulae 



on plate. 

 N. G. C. 4395-99, 4401. Remarkable spiral nebula, suggesting superposition of two 



sph'als, or a secondary center. 

 N. G. C. 4656-7. Right-handed spiral, one arm well defined, other diffuse. 

 N. G. C. 5278 and 5279. Two small left-handed spirals. 

 N. G. C. 5278-9. Right-handed spii-al with one arm. 

 N. G. C. 5868. Small round nebula. 

 N. G. C. 5869. Small elliptical nebula. 

 N. G. C. 6823. Cluster. 



N. G. C. 6927, 6928, 5930, etc. Field of 7 small spirals. 

 N. G. C. 7626, etc. Field of many small stellar and spiral nebulae. 

 I. C. 917-938. Field of many small nebulae. 



Slight changes have been observed in N. G. C. 1555, but none that 

 is certain in N. G. C. 2245. 



Mr. Sanford has made 6 photographs of Nova Aquilse No. 3, with 

 exposure times ranging from 75 to 390 minutes. No evidence of nebu- 

 losity about the star had been found up to June 1919, when the last 

 photograph was made. During 1918 the exposures were necessarily- 

 limited in length, owing to the brightness of the star. 



From a series of 18 photographs of the Andromeda Nebula, made on 

 Seed 30 plates with exposure times averaging about 30 minutes each, 

 Mr. Sanford has discovered 4 additional Novae, Nos. 10, 11, 12, and 

 13; a fifth Nova has been found by Mr. Duncan. 



Mr. Duncan has made 14 photographs of nebulae with the 60-inch 

 reflector, including exposures of 2 hours or more upon the objects 

 N. G. C. 6703, Messier 8, Messier 17, and Messier 31. 



STELLAR PARALLAXES AND PROPER MOTIONS. 



During the period September to June, Mr. van Maanen made 347 

 negatives with 510 exposures at the 80-foot focus of the 60-inch re- 

 flector; 267 of these, including 428 exposures, were made for parallax 

 measures, and 80, with 82 exposures, were made for the determination 

 of proper motions. During the absence of Mr. van Maanen in July 

 and August, Mr. Benioff made 62 negatives, 40 for parallax and 22 

 for proper motion, with a total of 92 exposures. 



Mr. van Maanen has completed the measures and reductions for 

 20 parallax fields, thus giving a total of 100 fields finished to date. 



The parallaxes of 3 additional planetary nebulae were also deter- 

 mined, viz, N. G. C. 6804, 6905, and 7008. The relative values 

 were found to be +0T020, +0':013, and +0''014, respectively. If 

 these results are combined with those for N. G. C. 2392, 6720, and 

 7662, given in the last report, we are led to the following conclusions 

 regarding these remarkable objects: 



The mean absolute magnitude of the central stars is +9.1. This is 

 noteworthy because the spectra of these objects consist in many cases 

 chiefly of bright lines, whereas, in the case of stars, bright-line spectra 



