Annals of the Astronomical Observatory of George-Town College, Containing the Description of the Observatory, and the Description and Use of the Trans

Annals of the Astronomical Observatory of George-Town College, Containing the Description of the Observatory, and the Description and Use of the Trans

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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. 1852 edition. Excerpt: ...4th or meridian wire in the above state of the Transit Instrument is greater than the time of transiting the true place of said wire, and consequently the correction must be subtracted or applied to the time of the passage of the object over the mean of the 7 wires with a negative sign, and for stars under or below the pole, which enter the field of view on the east side, the correction for collimation error must be applied with a plus sign--the reverse takes place if the meridian wire was on the west side of the true line of collimation; that is, an object observed above the pole will be seen on the 4th wire too soon, or before it gets to the true line of collimation, and consequently the correction for collimation error must be added or applied with a plus sign to the time of transiting the mean for the 4th wire, and applied with a negative sign for stars below the pole. In the figure, let a b f h i be the circle parallel to and on the west side of the meridian, that a straight line from the meridian wire through the centre of the object glass would describe when the Instrument is directed to southern horizon and moved through the zenith to the northern part of the horizon. It is evident from what has been said above that celestial objects will get to that circle before their image will appear on the meridian wire of the Instrument: now the arc Ha of the horizon or Ec of the equator is the angular measure of that circle from the meridian, and is also the angular measure of the meridian wire from the true line of collimation in the eye-piece, and is the error of collimation, . It is evident that the time a star takes to go from the meridian to the circle a b g hi in any parallel will be the correction due to collimation error; but it has been..show more

Product details

  • Paperback | 48 pages
  • 189 x 246 x 3mm | 104g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236525868
  • 9781236525864