This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1912 Excerpt: ...the instrument has a complete vertical circle and the time of culmination is known approximately, it will be well to eliminate instrumental errors by taking a second altitude with the instrument reversed, provided that neither observation is made more than 4TM or 5" from the time of culmination. If the star is a faint ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1912 Excerpt: ...the instrument has a complete vertical circle and the time of culmination is known approximately, it will be well to eliminate instrumental errors by taking a second altitude with the instrument reversed, provided that neither observation is made more than 4TM or 5" from the time of culmination. If the star is a faint one, and therefore difficult to find, it may be necessary to compute its approximate altitude (using the best known value for the latitude) and set off this altitude on the vertical arc. The star may be found by moving the telescope slowly right and left until the star comes into the field of view. Polaris can usually be found in this manner some time before dark, when it cannot be seen with the unaided eye. It is especially important to focus the telescope carefully before attempting to find the star, for the slightest error of focus may render the star invisible. The focus may be adjusted by looking at a distant terrestrial object or, better still, by sighting at the moon or at a planet if one is visible. If observations are to be made frequently with a surveyor's transit, it is well to have a reference mark scratched on the telescope tube, so that the objective may be set at once at the proper focus. The latitude is computed from Equa. 3 or 4. The true altitude h is derived from the reading of the vertical circle by applying the index correction with proper sign and then subtracting the refraction correction (Table I). The polar distance is found by taking from the Ephemeris (Table of Circumpolar Stars) the apparent declination of the star and subtracting this from 900. The image of a star is practically a point of light; if the telescope were perfect it would be actually a point, but, owing to the imperfections in the corrections for ...
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Add this copy of Text-Book on Practical Astronomy to cart. $21.67, new condition, Sold by Books2anywhere rated 5.0 out of 5 stars, ships from Fairford, GLOUCESTERSHIRE, UNITED KINGDOM, published 2022 by LEGARE STREET PR.
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Add this copy of Text-Book on Practical Astronomy to cart. $33.88, new condition, Sold by Books2anywhere rated 5.0 out of 5 stars, ships from Fairford, GLOUCESTERSHIRE, UNITED KINGDOM, published 2022 by LEGARE STREET PR.
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Add this copy of Text-Book on Practical Astronomy to cart. $37.30, new condition, Sold by Ingram Customer Returns Center rated 5.0 out of 5 stars, ships from NV, USA, published 2022 by Legare Street Press.
