instrument becomes wet, you should remove it from its carrying case and dry it thoroughly at room temperature once you get home. NEVER leave a wet instrument stored in the carrying case. NEVER rub the lenses of a telescope with your fingers or with a rough cloth. Clean chamois leather or a  lint-free  soft  cloth  is  suitable  for  this  purpose. Occasionally, you may clean the lenses with a soft cloth that is dampened with a mixture of equal parts of water and alcohol. You  should  always  remove  mud  and  dirt  from tripods,  range  poles,  leveling  rods,  and  so  forth, immediately after each use. This is very important, especially when the surveying gear is made of a material that is susceptible to rust action or decay. When lubricating instruments, you must use the right lubricant that is recommended for the climatic condition in your area; for instance, it is recommended that graphite be used to lubricate the moving parts of a transit  when  the  transit  is  to  be  used  in  sub-zero temperatures; however, in warmer climates you should use  alight  film  of  oil  (preferably  watch  oil). Consult the manufacturer’s manual or your senior EA whenever you are in doubt before doing anything to an  instrument. INSTRUMENT ADJUSTMENTS AND REPAIRS Making minor adjustments and minor repairs to surveying  instruments  are  among  the  responsibilities  of EA personnel. Minor adjustments and minor repairs are those that can generally be done in the field using simple tools.  Major  adjustments  and  major  repairs  are  those generally  done  in  the  factory.  If  the  defect  in  the instrument  cannot  be  corrected  by  minor  adjustment  or minor  repair,  do  not  attempt  to  disassemble  it;  instead, make   necessary   arrangements   for   sending   the instrument  to  the  manufacturer.  Most  surveying instruments are precision instruments for which major adjustments  and  recalibration  require  special  skills  and tools  that  can  be  provided  only  by  the  instrument company or its subsidiaries. INSTRUMENT ADJUSTMENTS As stated previously, adjustment, as used in this chapter, means the process of bringing the various parts of an instrument into proper relationship with one another.  The  ability  to  make  these  adjustments  is  an important qualification of any surveyor. To make proper adjustments, the surveyor should have the following knowledge: 1. They must be familiar with the principles upon which the adjustments are based. 2. they must know the methods or tests used to determine  if  an  instrument  is  out  of  adjustment. 3.  They  must  know  the  procedure  for  making adjustments   and   the   correct   sequence   by   which adjustments must be made. 4.  They  must  be  able  to  tell  what  effect  the adjustment of one part will have on other parts of the instrument. 5.   They   must   understand   the   effect   of   each adjustment upon the instrument when it is actually used for  measurement. Generally, instrument adjustments involve the level tubes, the telescope, and the reticle; for example, if one or both of the plate-level bubbles of an engineer’s transit are centered when the plate is, in fact, not level, the instrument is out of adjustment. An optical instrument equipped  with  vertical  and  horizontal  cross  hairs  is  out of  adjustment  if  the  point  of  intersection  between  the cross hairs does not coincide with the optical axis. If the reflected bubble on a Locke or Abney level is centered when  the  optical  axis  is  other  than  horizontal,  the instrument is out of adjustment. The process of adjustment chiefly involves the steps that are necessary to bring a bubble to center when it should be at center or to bring a cross-hair point of intersection  into  coincidence  with  the  optical  axis. Instrument  manufacturers  publish  handbooks containing  recommended  adjustment  procedures.  These are  usually  small  pamphlets,  obtainable  free  of  charge. The following discussion is intended to give you an idea of general instrument adjustment procedures. For adjusting your particular instruments, however, you should  follow  the  appropriate  manufacturer’s instructions. General Adjustment Procedures Instruments   should   be   carefully   checked periodically to determine whether or not they need adjustment. There is an adage that an instrument should be checked frequently but adjusted rarely. The basis for this adage is the fact that modern quality instruments get out of adjustment much less frequently than is generally believed;  consequently,  a  need  for  adjustment  is frequently  caused  by  a  previous  improper  adjustment that was not really required but resulted from errors in checking. 6-2