Astronomical instrument, filar telescope micrometer, brass / glass, used at Sydney Observatory, made by Merz and Sons, Germany, 1860-1878. A filar micrometer for use in conjunction with a telescope to make precise measurements. The filar micrometer is mounted on a graduated circle. A screw gauge at the top of the instrument turns a wheel with a graduated scale engraved into its surface. Below this is another screw gauge that moves a brass plate up and down. In the centre of the brass plate is the eyepiece for the micrometer. On the other side of the micrometer is a circular brass aperture that has been painted black. This can be removed to reveal a series of flat mirrors covering the conical shaped inside of the instrument. There is a hole with a screw fitting in the middle of the aperture.
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(Accession num: H10006)
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