46 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 



76 



additions to knowledge, stating where, when, how and what he 

 sees during a lunar eclipse. 



NOTE ON FIGURES 2 AND 3 



Figure 2 is a reduced half-tone reproduction of the original 

 lunar eclipse photograph made by J. H. Metcalf (258) at Taunton, 

 Mass., 1909 XI 26. The lens used was his 12-inch doublet; scale 

 of plate 93" = I mm.; exposure from 20 h. 13 m. 30s. to 21 h. 34 m. 

 COS., G. M. T. ; the telescope was guided on a star and the moon 

 allowed to trail through the earth's shadow between internal contacts. 



Fig. 2. 



Of course the shadow also trailed among the stars a little ; and 

 on the plate the moon, and the shadow taken at the moon's distance, 

 are displaced among the stars by parallax ; they being seen from 

 Taunton, N. 41° 54', with the moon's zenith distance changing from 

 52° to 66°, and not from the center of the earth. 



Figure 3 is a diagram on about the same scale as figure 2, roughly 

 showing these geometrical relations. The corners of the rectangle 

 of hour and declination circles were marked approximately on the 

 negative, and a blue print made; on this were drawn the necessary 

 lines, hour and declination circles, ecliptic and orbit, and the out- 

 line of the moon trail. On the orbit, the points a and /? are the 

 geocentric positions of the moon's center at beginning and ending 



