334 



VON AfiX 



Table I a 

 Celestial Objects Brighter than Magnitude Zero 



[chap. 16 



At mean opposition 

 Max. at elongation 

 At mean opposition 

 At mean opposition 

 Max. rings open at 

 opposition 



Objects Brighter than First Magnitude 



Max. at elongation 



a Data from Russell, Dugan and Stewart, Astronomy. Ginn and Company, Boston, 1926. 



system presently mounted on the Mark 19 meridian gyro. For example, it was 

 found that the observing skill needed to manipulate the adjusting screws while 

 the eye is being held at the eyepiece of a telescope, which does not share in the 

 pitching, rolling and yawing motion of the rest of the ship, is not inconsiderable. 

 The selection of objects near the zenith makes it necessary to use an elbow 

 eyepiece almost exclusively. A system in which the line of sight is taken along 

 the polar axis would be simpler both optically and mechanically, and, with 

 catadioptric optics, permit both the weight of the system and the excursions of 

 the eyepiece to be greatly reduced. 



As a by-product of the navigational experiments the meridian gyro apparatus 

 also made it possible to take 30-min exposures of star fields with small cameras 

 mounted on the hour circle box of the upper theodolite, the latter serving as an 

 equatorial mounting. The diurnal motion of the earth was cancelled by manual 

 operation of the hour-circle slow-motion screw and occasional corrections of 



