On either side of the arm 57 are switches 58 and 59 that are engaged by the arm 57 when the telescope 55 is swung through as small an arc as {HEAD ~ a fraction} of {TAIL ~ a degree} 
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On either side of the arm 57 are switches 58 and 59 that are engaged by the arm 57 when the telescope 55 is swung through as small an arc as { HEAD ~ a fraction } of { TAIL ~ a degree }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL