INSTRUCTIONS FOR MAKING PILOT BALLOON OBSERVATIONS 9 



ure 2, and adjust the shifting center S, so that the seats of the leveling 

 screws, LS, are symmetrically arranged over their respective plates 

 of the tripod head, T. After tightening the clamp ring to retain the 

 shifting center in that position, the tripod is in readiness for the 

 instrument itself. If the ti'ipod has the screw-thread type head it 

 is necessary only to unscrew and remove the cap to make it ready 

 for the instrument. 



17. With the older type of instrument it will be found that the 

 telescope has been removed from its bearings and packed in a separate 

 rack in the case above the carriage. When so packed, remove the 

 telescope rack and lower carriage from the case and remove the base 

 of the instrument from the lower shelf by unscrewing the thumb nut on 

 the underside. To place the telescope in position on the j^oke stand- 

 ard, remove the caps or cover blocks, C, set the telescope on the stand- 

 ard, and then replace the cover blocks. In this operation great care 

 should be taken that the screws or blocks are not interchanged. To 

 avoid this, markings have been made on the tops of the standards and 

 the bottoms of the blocks. See that these markings agree before 

 fastening the blocks on the standard. Make sure that the telescope is 

 firmly set in its bearings, replace the caps or cover plates in the same 

 position as that from which they were removed. Turn in the screws 

 firmlv, but do not force them. Under no consideration should the 

 leatherized bushing screw at th? middle of the cover plates, or the 

 Y-block screw on the underside of the left bearing, be touched at this 

 time. These materiallv affect the adjustment of the instrument and 

 should not be disturbed. (In packing the newer-type instruments the 

 telescope is not separated from the standard, and in unpacking them, 

 therefore, it is necessary only to slide out the shelf to which it is 

 attached and unscrew it from the shelf.) Next, replace the brass cap 

 on the object end of the telescope with the aluminum cjdiuder, or 

 sunshade, found in a back corner of the shipping case. The function 

 of this shade is to protect the object lens, and the instrument should 

 never be used without it. Direct rays of the sun or strong light will 

 cause the cement between the sections of the object lens to run to one 

 side, causing a "fern leaf," which interferes with the visibility through 

 the lens. The cap on the axis of the telescope, just above the right 

 horizontal tangent screw, is now removed. The eyepiece is taken 

 from its rack in the back of the shipping case, freed from its protecting 

 cap on the lower end, and is screwed to the axis of the telescope in 

 place of the cap which was just removed therefrom. On the newer 

 lightweight type of instruments the eyepiece is not removed in 

 shipping. 



18. The assembled instrument is now^ lifted from the supporting 

 rack and carefullv placed upon the tripod, making sure (on the old- 

 type instruments) that the chain and hook, p, figure 2, drop straight 

 through the hollow spindle of the shifting center, S7\ and that the 

 three leveling screws, LS. are properly seated in tlie grooves in the 

 respective arms of the shifting center plate. Insuring that the tension 

 nut is run down well to the knurled end of the spindle, the shifting 

 center tension, ST, is now raised until the threaded socket engages 

 the threaded end of the vertical axis, VA, and turned on securely. 

 The tension nut is then run up on the spindle to compress the spring 

 and hold the instrument firmly on the tripod. However, the nut 

 must not be run up too far, so that there is no room left between the 



