A new method for precise astro-azimuths |
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| Authors: | L A Kivioja |
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| Institution: | 1. Surveying and Mapping, Purdue University, 47907, West Lafayette, Indiana
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| Abstract: | The theodolite used in this method is completely leveled by using autocollimation from a free mercury surface. This eliminates the need for striding or hanging levels which are in conventional use to level the trunion axis of the theodolite. Mercury leveling is more accurate and can be performed in a much shorter time than leveling by the striding or hanging levels. In addition, this new method removes the unavoidable axis wobbles contaminating the observed horizontal angles between the star and the azimuth mark. The uncontrolled wobble errors affecting azimuths can be up to three arc seconds. The axis wobbles are removed by using autocollimation from an axis mirror which is perpendicular to the trunnion axis of the theodolite. Autocollimation coincidences from the mercury and from the axis mirror can be made within one or two tenths of an arcsecond. This new method and instrumentation surpasses the obtainable precision by the conventional first-order astro azimuth observations by reducing the unknown systematic wobble and level errors by one order of magnitude. |
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