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Position calculation of the hour axis The following page leads you to the calculation of the position of the hour axis. The detailed explanations are in the section Precise Polar alignment methods and after you entered the needed values in the appropriate form you receive the results within seconds and then you know where the hour axis points to and how much you should move it and in what directions. In case where it is necessary the refraction of the atmosphere is taken into account. This changes the zero point. Date and time are always local values of the time zone where the observatory is. If temperature and height above sea level are unknown enter 0o Celsius centigrade und 0 meter. In all cases it is required that you carry out a rough polar alignment. This step brings the hour axis in area with a radius of about 0.5o around the true celestial pole. The procedure is simple: Set the declination of the telescope to 90o and center Polaris by moving the hour axis' azimuth and elevation. After that move the hour axis according to the calculated values with the help of a calibrated eyepiece. In the case of the first four methods the measurement is carried out with one star. The movement in both directions is used to calculate the position of the hour axis. In the case of the method of E.S. King use Polaris to measure the movement. In case where you align the hour axis for the first time this is the most promising variant. In this variant the measurement field has to be aligned azimuthal. In this variant the measurement field has to be rotated by the amount which corresponds to the half the measurement duration. This method can be used everywhere in the sky with the exception of the celestial equator and the neighboring regions. The unobstructed view to the celestial pole is unnecessary. This method can be used everywhere in the sky. In the visual case the measurement is carried out with one star and its movement are measured twice.
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Comments, questions, corrections markus.wildi@one-arcsec.org |
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