## The Sextant and Its Applications: Including the Correction of Observations for Instrumental Errors, and the Determination of Latitude, Time and Longitude by Various Methods on Land and at Sea, with Examples and Tables ... |

### Other editions - View all

The Sextant and Its Applications: Including the Correction of Observations ... W. H. Simms No preview available - 2017 |

### Common terms and phrases

apparent zenith distance approximate Arcturus artificial horizon assumed azimuth c₁ c₂ celestial object centre coefficient coincidence of images colatitude compute cos² derived determine difference direct and reflected direct image double altitude employed equation equatorial horizontal parallax example eyepiece formula geocentric glass Greenwich mean Greenwich sidereal Hence horizon-glass hour-angle index-glass instrument interval latitude likewise limb local sidereal log cos log sin longitude lunar distance Lyrę meridian passage method middle minutes moon moon's nearly objects observed observed altitude obtained operator optical axis plane polar distance position prime vertical quantities radius rays reflected images refraction result right angles right ascension second object semidiameter Sextant shade sin² star sun's supposed surface t₁ tabular telescope tion treated true zenith distance u₁ variation vernier w-wo w₁ w₂ watch Ž.sin αμ µ²

### Popular passages

Page 58 - The geocentric latitude is the angle between the plane of the equator and the line joining the place to the centre of the earth.

Page iii - ... their meshes, ganglionic cells.1 This observation is certainly one of the most remarkable on record, and, from the extraordinary character of its results, would hardly be accepted for a moment, but for the established reputation of Prof. Voit. As it is, such an observation demands full confirmation. It is well known to all who have been in the habit of removing the cerebral lobes, that it is absolutely necessary to remove every portion of their substance, in order to obtain uniform results, and...

Page 2 - Now it will be obvious that if the mirror b be made to revolve upon an axis at right angles to the plane of the paper, the original direction ab of the ray which, after two reflexions, is seen to coincide with the direct ray, will vary ; in other words, the angle between the original directions of the two rays and that between the surfaces of the mirrors are dependent one on the other. To determine the connexion between them, produce AB, ab to meet in E, and pb, BP to meet in P.

Page 72 - THE object of these Tables is to give the true correction of a lunar distance in all cases when, with the apparent distance of the moon from the sun, a planet, or star, the apparent altitudes of the two objects have also been obtained by observation. They enable us readily to take into account, — 1st, the parallax of the moon in the latitude of the observer, allowing for the spheroidal figure of the earth; 2d, the parallax of the sun or a planet...

Page 2 - Suppose two systems of parallel rays, each parallel to the plane of the paper, the one in the direction of AB, the other in that of a b. Let rays of the system parallel to ab fall upon a plane-reflecting surface b, this surface being at right angles with the plane of the paper.

Page 2 - B, this surface likewise being at right angles with the plane of the paper, and BP perpendicular to it. The second reflexion will be in the direction BE, BE being in the plane of the paper, and the angle...

Page 76 - ... distance, or as it is commonly termed clearing the distance, has been explained. Let T be the true place of the moon's centre as seen from the centre of the earth, and R that of the sun ; then TR is the true distance of the centres, which corresponds to the distances put down in the NauticalAlmanac, and from which Greenwich mean time is determined. The arc MT is part of a vertical circle ZT, and is the excess of parallax in altitude above refraction, by which the...

Page 43 - Elongation is oselul in setting the instrument for the observation. Without knowledge of the latitude the Azimuth may be obtained from two observation?

Page 115 - ... is the solar energy in langleys per minute on a given surface.6 For the values given by (3) to be geographically useful, they must be evaluated over periods of time during which both h and dA will be changing. To calculate and sum these values over small time intervals is an...

Page 73 - ... 7. The latitude is shown directly on the vertical scales at either side and is picked off as on any Mercator chart. Example. — Any time, at any place, observed the altitude of Arcturus to be 27°25...