DIY History | Transcribe | Scholarship at Iowa | Theory of the astronomical transit instrument applied to the portable transit instrument Wuerdemann no.26: a compilation from various authorities, with original observations by Harry Edward Burton, 1903 | Theory of the astronomical transit instrument applied to the portable transit instrument Wuerdemann no. 26: a compilation from various authorities, with original observations by Harry Edward Burton, 1903, Page 15

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Theory of the astronomical transit instrument applied to the portable transit instrument Wuerdemann no.26: a compilation from various authorities, with original observations by Harry Edward Burton, 1903

Theory of the astronomical transit instrument applied to the portable transit instrument Wuerdemann no. 26: a compilation from various authorities, with original observations by Harry Edward Burton, 1903, Page 15

Illumination
The wires are rendered visible in the day time by the light of day: but for observations at night, they are illuminated by means of a small lantern placed at one end of the axis. The light enters the opening of the axis and [?] a small mirror placed at the intersection of the axis and telescope. The mirror, being inclined at an angle of 45 degrees to the axis and telescope, then reflects the light down upon the reticle and [?] the field of view. The wires are then seen as dark lines on a bright field. 
Just enough light should be admitted to enable the observer to see the wires distinctly when taking [?] of faint stars, or they will be eclipsed by the light.
With some instruments these are two lanterns, or lamps, one at each end of the axis. In this case the unequal heating and consequent unequal expansions of the two [pivots?] is to a great extent avoided, and so is the inconvenience of changing the lantern from one side to the other when the instrument is reversed.

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Illumination The wires are rendered visible in the day time by the light of day: but for observations at night, they are illuminated by means of a small lantern placed at one end of the axis. The light enters the opening of the axis and [?] a small mirror placed at the intersection of the axis and telescope. The mirror, being inclined at an angle of 45 degrees to the axis and telescope, then reflects the light down upon the reticle and [?] the field of view. The wires are then seen as dark lines on a bright field. Just enough light should be admitted to enable the observer to see the wires distinctly when taking [?] of faint stars, or they will be eclipsed by the light. With some instruments these are two lanterns, or lamps, one at each end of the axis. In this case the unequal heating and consequent unequal expansions of the two [pivots?] is to a great extent avoided, and so is the inconvenience of changing the lantern from one side to the other when the instrument is reversed.