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 {HEAD ~ as small an arc} as a fraction of {TAIL ~ a degree} 
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 { HEAD ~ as small an arc } as 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 HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL