## A Text-book of Field Astronomy for Engineers (Google eBook) |

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adjustment almanac approximate ascension and declination assumed azimuth bubble readings celestial sphere centre chronometer correction Circle L circle readings collimation column computed constant convenient corre corresponding derived determined difference diurnal diurnal motion earth effect eliminated engineer's transit equal equation factors formulae fundamental plane furnished given gradienter Greenwich Greenwich Mean horizontal axis horizontal circle hour angle index-glass instru interpolated latitude level correction level error line of sight logarithms longitude mark mean solar measured ment meridian method micrometer minutes motion observations observer's obtain parallax perpendicular Polaris pole position precision prime vertical quadrant quantities reduction refraction relation represent reversal right ascension rotation axis screw sec h sextant sidereal spherical angle spherical triangle star's student subtract sun's Table telescope theodolite thread tion transit instrument true tube vernal equinox vernier vertical axis vertical circle watch zenith distance zenith telescope

### Popular passages

Page 4 - A cos 6 = cos a cos c + sin a sin c cos B cos c = cos a cos 6 + sin a sin 6 cos C Law of Cosines for Angles cos A = — cos B...

Page v - It seems to be the duty of the instructor to select for presentation those parts of astronomical practice most closely related to the work of the future engineer, and. with reference to the narrow limits of time allotted the subject, to keep m the background many collateral matters that are of primary interest and importance to the student of astronomy as a science.

Page 30 - If the mean time of upper culmination is not known, the time of either elongation may be determined as follows: To the sidereal hour angle of the star add the right ascension of the star. The result is the sidereal hour angle of the vernal equinox or the right ascension of the meridian or the sidereal time at elongation, all of which amount to the same thing.

Page 110 - Next, the bubble being at the middle of its tube, carefully lift the telescope out of the wyes, turn it end for end, and replace it. If the bubble...

Page 40 - ... we must convert our watch time into solar time before we are to use the tables. We must then hunt up an almanac and find the equation of time for that particular day, and if we are going by standard time we must still further combine the result for this difference. But, owing to the daily change of the equation of time (the sun fast...

Page 39 - ... is divided into equal parts, and all mean solar days are exactly the same length. A true solar day is the time between two successive passages of the sun across the zenith. On account of the elliptical shape of the earth's orbit and its inclination to the earth's axis these true solar days vary in length, a day in December being nearly a minute longer than one in September. The accumulation of these differences may make the time of the passage of the sun across the zenith (noon by true solar...

Page 132 - The rotation axis and the plane of the index -glass must be perpendicular to the plane of the graduated arc.

Page 23 - That vertical circle whose plane is perpendicular to the meridian is called the prime vertical.

Page 135 - Using an artificial horizon, bring the direct and reflected images of the sun externally tangent to each other in each of the two possible positions...

Page 137 - The reflected image of the sun or star lies as much below the true horizon as the real object is above it...