MISCELLANEOUS PAPERS. 23i 



THE ELEVEN-AND-ONE-HALF-INCH EQUATORIAL 

 TELESCOPE, 



WASHBURN COLLEGE OBSERVATORY. 



By H, L. Woods, Washburn College, Topeka. 

 Read before the Academy, at Topeka, January 1, 1903. 



'T^HE telescope lately erected in the new observatory of Washburn 

 ■^ College is of very moderate size when compared with the many 

 large instruments. However, it is hoped that a short description of 

 it may be not entirely without interest. The objective has a clear 

 aperture of 11| inches and a focal length of 165 inches. The form 

 of the lens is of the Herschel pattern, with no air space except that 

 due to variation in the curvature of the surfaces. The glass was fur- 

 nished by Mantois, of Paris, who also furnished the glass for the Lick 

 and the Yerkes objectives. The lens was ground by Brashear, of 

 Allegheny, Pa. There are five eyepieces, of the following powers : 

 120, 165, 220, 330, and 715. A helioscopic eyepiece is provided, and 

 a wide-angle comet eyepiece of 150 power. The finder has an aper- 

 ture of three inches and a power of twenty. 



The column to the top of the declination head is ten feet in height. 

 It is made in three sections, including the declination head. On the 

 inside of the base, near the bottom, are cast lugs to support a floor of 

 wood and concrete, which effectually prevents air currents from pass- 

 ing through the column. This has been found to be a protection to 

 the clock in frosty weather, where, as is the case with this instrument, 

 there is an open air space below the base. The second section con- 

 tains the driving clock, and carries on its north side the R. A. dial 

 and reading microscopes for the fine hour circle. The two sections 

 of the column proper and the declination head are rigidly bolted to- 

 gether. Their aggregate weight is 2350 pounds. 



The thrust at the lower end of the polar axis is taken by ball bear- 

 ings in phosphor-bronze casings. The upper end of the axis is carried 

 by a phosphor-bronze bearing. The friction at this point is relieved 

 by anti-friction rollers. The polar axis terminates in a head to which 

 is attached by heavy screws the declination sleeve. Through this 

 sleeve runs the declination axis, which in turn contains the rods for 

 operating from the eye end of the telescope tube the clamp and slow 

 motion on the polar axis. 



The tube is of steel sheets closely riveted. The main draw-tube 

 for focusing is operated by rack and pinion and carries a smaller draw- 

 tube, Both tubes are provided with scales for locating proper posi- 



