Book Description

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1894 edition. Excerpt: ...exactness the moment when the observation should be made. Stormy weather, a hazy atmosphere, or the presence of clouds, may interfere with or entirely prevent observation when the star is either at elongation or on the meridian, and both events sometimes occur in broad daylight or at an inconvenient hour of the night. Under such circumstances, a simple method applicable at any time (Polaris being visible), may be acceptable, and can often be used by the surveyor when other methods fail. DETERMINATION OF THE AZIMUTH OP POLARIS AND TRUE MERIDIAN AT ANY HOUR, THE STAR BEING VISIBLE, AND THE CORRECT LOCAL MEAN TIME BEING KNOWN. Many years ago a table was published giving azimuths of Polaris at stated times during one year, but as it was arranged for a kind of time with which surveyors are generally unacquainted, and was explained in unfamiliar astronomical terms, and required the use of tables and data not always accessible, it met with little favor and never came into general use. In this article it is proposed to simplify the work, omit all technicalities requiring a knowledge of astronomy, and present the method, with two new and compact tables adapted to common clock time, with such plain directions for use that any person of ordinary intelligence can understand and apply them. As the surveyor should have a perfectly clear idea of what is meant by Astronomical Time (used to simplify computations), and the Hour A ngle of Polaris, these terms will now be explained. The Civil Day, according to the customs of society, commences at midnight and comprises twenty-four hours from one midnight to the next following. The hours are counted from 0 to 12 from midnight to noon, after which they are again reckoned from 0 to 12 from noon to midnight....