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LEFT SEARING A See also: rubber guard is fitted round the See also: eye-pieces
.
Its functions are to guide the eyes of the observer into the correct position, and to protect them from See also: side See also: light and the distressing effect of See also: wind
.
It also See also: guards the forehead against the See also: jar occasioned by firing heavy guns
.
The upper portion of the See also: field presented to the left eye is used as a finder, the
See also: lower portion is occupied by the See also: scale upon which the ranges are engraved
.
The finder is a low-power See also: telescope of large field, to the centre of which the See also: objective is brought
.
When the telescope is thus correctly aligned, the objective will be seen with the right eye largely magnified, but as two partial images separated by a thin black See also: horizontal See also: line
.
When coincidence of the images is effected by means of the working See also: head, the range can be
2 The length of See also: tube varies from 3 ft. in the smaller to 9 ft. in the larger See also: instruments
.
i
read off against a pointer from the scale seen with the left eye
.
For 1 or on different parts of the same objective, and thus inaccuracy in the See also: night use, means are provided for See also: illuminating the scale
.
The range recorded-range must result
.
The instruments are expected to give an to See also: lights may be ascertained by the use of the astigmatizer, an See also: optical accuracy of less than
See also: device by which a point of light is See also: drawn out into a vertical streak
.
2 % at 2000 yds
.
For A*,ogjectioe A See also: beam of light from the objective falls on each reflector (fig
.
2), ranges over that distance, i.e. for usual
DOW uFPORT /IMDER See also: OBJECT See also: GLASS SUIMORT WINDOW
RE n artillery ranges, it is
IRATE
WIN ) See also: FRAME EYE PIECE PRIS5S-W SCALE ass desirable to use a
ccro OBJECT GLASS See also: CASE >rZn 'redouble See also: base (1oo yds
.
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[back] TANNEGUY LEFEBVRE (TANAQUILLUS FABER) (1615-1672) |
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