 | John William Norie, J. W. Saul - Nautical astronomy - 1917 - 642 pages
...instrument, and their planes parallel to each other when the index-division is at o on the arc ; also, to set the axis of the telescope parallel to the plane of the instrument ; each of these particulars must be examined before an observation is taken, and the adjustments, if... | |
 | Brian Lasater - History - 2008 - 600 pages
...should be adjusted by means of screws attached to it. (d) The fourth adjustment consists of making the axis of the telescope parallel to the plane of the instrument. To do this, a telescope containing two parallel wires is used. Screw in the telescope so that the two... | |
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... instrument is out of adjustment in this respect, the direct and reflected images will not coincide, but the reflected image, as the arm moves, will be slightly above or below the direct image. Adjust the horizon-glass so that the two images coincide... 
