For reducing the Sun's Right Ascension in Time, as given in the Nautical Almanac for Noon at Greenwich, to any other Time under that Meridian; or to Noon under any other Meridian

2014 ◽  
pp. 158-160
Author(s):  
Nevil Maskelyne
Keyword(s):  
Right Ascension ◽  
Nautical Almanac

The Earth's Magnetic Field

1950 ◽  
Vol 3 (1) ◽  
pp. 1-9
Author(s):  
Harold Spencer Jones
Keyword(s):  
Magnetic Field ◽  
High Speed ◽  
Spherical Triangle ◽  
Basic Data ◽  
Earth’S Magnetic Field ◽  
Wide Range ◽  
Earth's Magnetic Field ◽  
The Many ◽  
Right Ascension ◽  
Nautical Almanac

The Institute has now completed two years of its existence. The papers which have been read before it during these two years have covered a wide range of subjects and have served to emphasize the many ramifications of the science of navigation. Because of the high speed of modern aircraft, air navigation presents more problems and of greater variety than surface navigation, but even on the problems of surface navigation there has been ample scope for a wide range of discussion. The Institute has taken a prominent part in the discussion of the proposals for the revision of the Abridged Nautical Almanac. It might with some reason have been supposed that there was nothing more to be said on the methods of reducing astro-sights and determining position at sea. The problem is perfectly straightforward and there is a limit to the number of different ways in which the spherical triangle can be solved. But the essential basic data can be presented in a variety of ways, while there are many possible methods of presenting tables for the solution of the spherical triangle. The decision to use Greenwich hour angle instead of right ascension in the Abridged Nautical Almanac has followed its adoption in the Air Almanac; the revised Almanac will have an entirely different format from the present, while the methods of reducing sights must be correspondingly modified.

The New Abridged Nautical Almanac

1951 ◽  
Vol 4 (04) ◽  
pp. 377-385
Keyword(s):  
Present Form ◽  
Transitional Period ◽  
The Sun ◽  
American Spanish ◽  
Detailed Work ◽  
Right Ascension ◽  
Nautical Almanac

TheAbridged Nautical Almanacin its revised form, for the year 1952, has now appeared. In place of right ascension and the familiar quantitiesEandRwhich were adopted in 1929, it tabulates Greenwich hour angle in arc for the Sun, Moon, planets and Aries, and sidereal hour angle (or versed ascension) for the stars.Greenwich hourangle has been used in air almanacs for a number of years, and several surface almanacs have tabulated it as an alternative to right ascension; it is only recently, however, that it has been given exclusively in surface almanacs. Among the surface almanacs which tabulate G.H.A. at present are the American, Spanish, Argentine, Brazilian and Yugoslav.The redesign of theAbridged Nautical Almanachas been under consideration for many years, but the change was delayed first by the war, and then by the desire to avoid a transitional period during which the new G.H.A. andEandRwere given together; it was also decided to give as much notice of the proposed changes to users as possible. The design in substantially its present form was in fact accomplished in 1947, though the arrangement of the daily pages and much detailed work was carried out later.

A Device to Determine Position Rapidly Without Calculation

1956 ◽  
Vol 9 (1) ◽  
pp. 11-16
Author(s):  
Leo Randić
Keyword(s):  
Sidereal Time ◽  
Outer Circle ◽  
The Earth ◽  
Geographical Latitude ◽  
The Difference ◽  
Celestial Sphere ◽  
The Right ◽  
Right Ascension ◽  
Nautical Almanac

The problem of the determination of the observer's position on the Earth can be most easily solved in terms of the equatorial coordinates of the observer's zenith. From Fig. 1, in which the inner circle represents the Earth and the outer circle the celestial sphere, it can be seen that the zenithal point on the celestial sphere is its intersection with the prolongation of the radius to the observer's position. The geographical latitude of the observer is equal to the declination of the observer's zenith, and the geographical longitude is equal to the difference between Greenwich sidereal time (G.S.T.) and the right ascension of the observer's zenith. We can obtain G.S.T. by interpolation from a nautical almanac or directly from a separate watch or clock set to keep sidereal time.

scholarly journals Remarks on a correction of the solar tables required by Mr. South’s observations

1833 ◽  
Vol 2 ◽  
pp. 305-305
Keyword(s):  
The Sun ◽  
Peculiar Form ◽  
The Mean ◽  
Right Ascension ◽  
Nautical Almanac

The discordancies observed by Mr. South between the sun’s right ascension, as deduced from observation, and those given in the Nautical Almanac, follow a law so simple as not to allow of their being regarded as errors of observation, or arising from any casual cause, but justify us in attributing them to imperfections in the solar tables, with the exception of three days, in which there seems to be some ground to suspect error of computation. A single inspection of these discrepancies, Mr. Airy observes, suffices to show that they arise almost entirely from an error in the epoch, and an error in the place of the perigee. From the peculiar form of the tables in Vince’s Astronomy, which give great facility to the introduction of an error in the excentricity, he was induced at first to suspect that one might exist; but on calculation found the error in the equation of the centre so small as to be entirely insensible. He then proceeds to detail the process by which, from Mr. South’s observations, he has deduced the amount of the several errors, which consist in regarding the epoch, the mean anomaly, and the equation of the centre, as erroneous by three very small unknown quantities, and forming as many equations of condition for determining them as there are observations. These combined and resolved, so as to give the most probable result, lead to the conclusions, first, that the correction of the equation of the centre is evanescent; secondly, that the epochs of the sun must all be increased by 9", and the epochs of the perigee each by 1' 48".

2. Solar Eclipse, 31st December 1880

1882 ◽  
Vol 11 ◽  
pp. 18-19
Author(s):  
E. Sang
Keyword(s):  
Solar Eclipse ◽  
The Sun ◽  
Actual Observation ◽  
Lunar Ephemeris ◽  
The Times ◽  
The Right ◽  
Right Ascension ◽  
Nautical Almanac

The elements for the compution of eclipses are given in the “Nautical Almanac” with precision sufficient for all ordinary purposes; but, when we wish to compare the lunar ephemeris with actual observation for the purpose of verifying or of improving our data, we must go somewhat more minutely into the investigation.Thus, in the List of Elements, p. 403, the changes in the right-ascension and declination of the sun and moon are supposed to be proportional to the times, while the moon's geocentric semidiameter, as well as the horizontal parallax, is supposed to be constant during the eclipse. In this way some exceedingly small errors are introduced into the calculation.

Astronomical observations

1833 ◽  
Vol 2 ◽  
pp. 135-135
Keyword(s):  
Direct Method ◽  
The Sun ◽  
Vernal Equinox ◽  
Astronomical Observations ◽  
The World ◽  
The Mean ◽  
The Right ◽  
Right Ascension ◽  
Nautical Almanac

In the present improved state of astronomical observations, it is material to possess the readiest and most accurate means of finding the apparent time. The right ascension of certain fixed stars having been precisely obtained relatively with each other, and with the equinoctial points during the course of many years, affords the direct method of ascertaining the right ascension of the mid-heaven: hence the convenience of having the corrections of these stars in the form of tables, that the same may be taken out at one view with the arguments of the sun’s longitude, and of the moon’s node. For this purpose the mean diurnal motion is adapted to the longitude of the sun, as found in the Nautical Almanac, at the time the star passes the meridian. The mean epoch is reduced to the vernal equinox less four seconds, in order to render the corrections additive; which, being an universal period, the same applies to all parts of the world. To these tables Mr. Groombridge has subjoined some observations of the planets at and near the oppositions; also of the solstices of the last two years, and of the comet of 1819.

On the possible gamma-ray source in Cygnus

1967 ◽  
Vol 31 ◽  
pp. 469-471
Author(s):  
J. G. Duthie ◽  
M. P. Savedoff ◽  
R. Cobb
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
Right Ascension

A source of gamma rays has been found at right ascension 20h15m, declination +35°, with an uncertainty of 6° in each coordinate. Its flux is (1·5 ± 0·8) x 10-4photons cm-2sec-1at 100 MeV. Possible identifications are reviewed, but no conclusion is reached. The mechanism producing the radiation is also uncertain.

Fundamental observations made at Breslau in 1922-1925

1978 ◽  
Vol 48 ◽  
pp. 433-435
Author(s):  
F. Schmeidler
Keyword(s):  
The Sun ◽  
Vertical Circle ◽  
Right Ascension

Meridian observations of fundamental stars were made at Breslau Observatory in 1922 to 1925. The observations in right ascension were made by W.Rabe with the 6-inch transit instrument, whereas the declinations were observed by A.Wilkens with the vertical circle. In both coordinates, observations of the Sun were also made.

Systematic effects in observed parallaxes

1978 ◽  
Vol 48 ◽  
pp. 31-35
Author(s):  
R. B. Hanson
Keyword(s):  
Error Estimates ◽  
Zero Point ◽  
Absolute Zero ◽  
Apparent Magnitude ◽  
Coherent System ◽  
Preliminary Results ◽  
General Catalogue ◽  
Systematic Effects ◽  
New Evidence ◽  
Right Ascension

Several outstanding problems affecting the existing parallaxes should be resolved to form a coherent system for the new General Catalogue proposed by van Altena, as well as to improve luminosity calibrations and other parallax applications. Lutz has reviewed several of these problems, such as: (A) systematic differences between observatories, (B) external error estimates, (C) the absolute zero point, and (D) systematic observational effects (in right ascension, declination, apparent magnitude, etc.). Here we explore the use of cluster and spectroscopic parallaxes, and the distributions of observed parallaxes, to bring new evidence to bear on these classic problems. Several preliminary results have been obtained.

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