Surveying Manual ; a Surveying by William David Pence

Author:William David Pence
Language: eng
Format: epub
Publisher: McGraw-Hill book company, inc.
Published: 1915-03-25T05:00:00+00:00

Tig. 23b.

the following relations: (1) The polar axis should be perpendicular to the line of collimation of the solar telescope and the horizontal axis of the main telescope; (2) the tine of collimation of the solar telescope and the attached level line should be parallel. The methods of making these ad' justments are obvious.

The declination of the sun (see Fig. 23b for explanation of astronomical terms) for the place of observation is found by adding, algebraically, the hourly change multiplied by the number of hours since Greenwich mean noon (6 A. M., 90th Meridian) to the declination of the sun, aa given in the solar ephemeris for Greenwich mean noon for the given date. The isetting (apparent declination) is found

hy taking the algebraic sum of the refraction correction and the declination of the sun obtained aa ahove. The refraction is always plus; the declination is plus when the sun Is north and minus when south of the celestial equator; and the hourly change in declination is plus when the sun Is moving north and minus when moving south.

The " Pocket Solar Ephemeris and Refraction Tables for Use with Saegmuller's Solar Attachment," is given in " Handbook for Engineers " by George N. Saegmuller, published by Bausch & Lomb Optical Co., Rochester, N. Y. An " Ephemeris of the Sun and Polaris, and Tables of Azimuths of Polaris " is published by the General Land Office for each year. This Ephemeris may be obtained by addressing the Department of Interior, General Land Office, Washington, D. C, or may be purchased at a price of 5 cents per copy from the Government Printing Office, Washington, D. C. The true local mean solar time should always be used, and may be obtained from standard or railroad time by adding or subtracting four minutes for each degree that the place of observation is east or west of the standard meridian. The mean refraction of the sua for different altitudes ia given In Table V.)

TABLE V.

Mean Repeaction ov the Sun,

Baboueteb 30 Inches, Tbupebature 50° Fah>,

(Refraction makes observed altitude too large.)

(1) Calculate the apparent declination (setting) of the sun for several different times, varying by 15 minutes, between 8 and 10 o'clock A. M. and 2 and 4 o'clock P, M. (2) Set the transit over the hub, level up very carefully with the attached bubble, and very carefully adjust the noain transit and solar attachment. Determine the index error of the vertical circle, and either correct it or apply it to all vertical angles with its proper sign. (3) Level the transit

THE TRANSIT.

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