Ebook Astronomical Observations Made at the Royal Observatory, Edinburgh

The process of reversing the instrument is conveniently and safely per formed by means of an apparatus, which allows the counterpoises to act before the pivots touch the Y's, so that no additional pressure is exerted upon them, and the instrument is replaced without the least collision. Five vertical Wires and one horizontal Wire of spider-thread are placed in the eye-end of the telescope, besides other two vertical Wires, which are fixed to the same frame, and move together by means of a micrometer screw. The Telescope has four eye-glasses, whose magnifying powers are 100, 136, 200, and 300; but 200 is the power commonly used. For faint objects, the power 136 is applied. The whole aperture of the object-glass is employed, ex cept in observations of the Sun, when it is contracted to inches, and the ih strument screened from the solar rays.