Precession Constant Research Articles

Short-Period Nutation from Observation with the Pulkovo Polar Tube

Since 1953 regular observations have been made with the polar photographic tube at Pulkovo, a fixed astrograph (D = 20 cm, F = 600 cm), which can take photographs of a circumpolar zone of 60′ radius (Bakhrakh, 1971). An analysis of measured polar distances of the same 30 stars on each plate gives corrections to the adopted values of the constants of aberration and precession and of the coefficients of nutation. At present the determination of the coefficients of the short-period semi-annual solar and fortnightly nutations is of greatest interest, as they are affected most by the Earth's liquid core.

The continuous pattern of variations of the geomagnetic field in the quaternary and their causes

Apart from a brief account of the theories of the geomagnetic field and from suggestions of obtaining new data, the present work contains an analysis of the results of investigations into continental Quaternary sediments, which have become the object of close palaeomagnetic studies in Czechoslovakia in recent years. Besides sea sediments they represent one of the few possibilities of obtaining more complete data on the past of the geomagnetic field even though their investigation requires instruments of high sensitivity and exact processing technique. A brief geological description and chronological list of individual sedimentary cycles are presented and the results of their palaeomagnetic investigation on a number of samples (about 2 000) are given. The obtained results suggest that the geomagnetic field probably displayed successive changes in the position of its magnetic axis shifting from the region of the south pole to the region of the north pole over a period of approximately 2.5 millions of years in the form of oscillations caused by impulses recurring at periods of about 140 000 years. Three types of changes of the geomagnetic field with different periods can be identified (Fig. 2): not always expressive changes with the period of 2.5 × 10 4 years, quasisinusoidal changes with a period of about 1.4 × 10 5 years and long-term changes most likely also periodical with the period of about 2.5 × 10 6 years. The first and the second periods, particularly, are close to the precession constants as far as the magnitude is concerned. Thus it can be stated that the differences in the precession rates of the motion of the core and the mantle may markedly act together in the origin of the geomagnetic field.

Proceedings of IAU Colloquium No. 9, The IAU System of Astronomical Constants, Heidelberg, 12-14 August 1970

The principal purpose of IAU Colloquium No. 9 on the IAU System of Astronomical Constants was to discuss whether further action should be taken to revise those fundamental constants (namely the constants of precession and nutation and the system of planetary masses) that were left unchanged when new values of the other constants were adopted at Hamburg in 1964. The opportunity to discuss other relevant matters was also taken.

Development of a catalogue of galactic x-ray sources

view Abstract Citations References (4) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Development of a catalogue of galactic x-ray sources Ouellette, Gerald A. Abstract Proper motions of stars may be obtained with reasonably good accuracy from the combined entries of several old position catalogues. The procedure followed by Dr. Gale W. Cleven (1962) in his dissertation at Georgetown Observatory (Georgetown Observatory Monograph No. 18) involved two steps, one, in which the original published positions were reduced to the system of the General Catalogue with the aid of formulas given in the GC; in the second step the positions for each catalogue were reduced to a uniform precession constant and brought forward to a single epoch (1900.0). The individual positions at the common epoch were assumed to differ only by the accumulated proper motion. With the advantage of large computers with which the corrections can be applied quickly and the results tabulated automatically, this procedure can provide proper motions that will add significantly to the available data for dynamical and statistical studies. Granted that old position catalogues are unsuitable for systems comparable to the FK3, FK4 and later systems, the 1456 proper motions obtained by the above procedure for a small area of the sky in Orion have an accuracy comparable with values given in the GC and Yale Catalogue. Publication: The Astronomical Journal Pub Date: June 1967 DOI: 10.1086/110278 Bibcode: 1967AJ.....72..597O full text sources ADS |

The Reduction of Radio Source Positions to Standard Epoch

The usual method of calculating corrections for precession nutation and aberration involves the use of the precession constants M, N, m, n and the Day Numbers A, B, C, D, E, J, J’. For the computer analysis of radio source data obtained with the Molonglo Telescope it seemed desirable to compute the corrections directly from the basic formulae, thus avoiding the trouble and possibility of accidental error in copying out the Day Numbers for each day’s observation. In this paper we quote in full the equations that are used in the analysis of the Molonglo data. These equations are abstracted from The Explanatory Supplement to the Astronomical Ephemeris and Smart’s Spherical Astronomy, and expressed in a form which parallels the organization of the computer routine. In addition to the observed position, the only other data required to compute the precession nutation and aberration corrections is the Julian date (J.D.). This basic parameter in the equations is very simply calculated to the required accuracy of a few minutes from the time and date of the observation. The computer routine that computes the corrections occupies 1350 words of programme in the KDF9 computer and takes 200 msec to compute one position. If a large number of computations are being carried out on continuous data, then the average time per computation is only 5 msec as a full computation of the coefficients does not have to be made for each point separately.

New impetus to astrometry

In 1964 a conference was held at Flagstaff, Arizona, in honour of Ejnar Hertzsprung. At this conference Martin Schwarzschild presented the inaugural address. The title was 'New Impetus to Astrometry'. I was so much impressed by everything what he, as an astrophysicist, had to say that I have always remembered his analysis of important astrometric problems with admiration. Nine years after the Flagstaff Conference, I find it appropriate to open this Symposium in referring to Schwarzschild's lecture and in presenting my views on recent developments and on progress which I expect in the future. Major achievements in astrometry during the past decade resulted mainly from the introduction and development of new instrumental techniques, the application of astrometric methods in new areas of astronomy, and from the vigorous and successful work in large international undertakings. An important part of the recent progress was unforeseen, namely, the progress made in the absolute measurement of positions of objects by means of radio techniques. Let us first consider the classical areas of astrometry. I will follow here Schwarzschild in first citing the determination of the local inertial frame of rest, which in practice, is given by a system of positions and proper motions of fundamental stars and the knowledge of accurate values of the so-called constants of precession, nutation and aberration. While in 1963 the Fourth Fundamental Catalogue {FK4} was completed on the basis of observations before about 1950, an enormous effort began with the aim of improving the system and the individual data of the FK4. The observations have been carried out with the transit circle, the vertical circle, and with Danjon's astrolabe. By means of improved techniques the errors of observations have been decreased by a factor of about two compared with the observations on which the FK4 was based, and it has become possible to push the magnitude limit of meridian circles to stars fainter than visual magnitude nine. Furthermore, considerable contributions have been made to the improvement of the system in the southern sky, which in the FK4 was based almost entirely on observations made at the Cape Observatory alone. The number of absolute and differential observations made since 1950 is already sufficiently large to justify an extensive analysis with the aim of an improvement of the FK4 and its extension from magnitude 7.5 to 9.0. Progress has also been made in determining precession. It has become clear that Newcomb's planetary precession requires a small correction due to recent improvements of the values of the planetary masses. The point has been reached where further correc-

Inaugural address Delivered at the I.A.U.-Symposium no. 21

After a presentation of the problem posed by the construction of a system of astronomical constants, the author describes the new catalogue FK 4. He then reviews recent progress in the knowledge of the orbits of major planets and in the determination of solar parallax, the constant of aberration and the constant of precession.

The precessional constant, parameters of solar motion and galactic rotation in the FK 4 system

In this paper, an investigation is made of the changes in the constant of precession, parameters of solar motion and of galactic rotation, caused by the transition from the FK 3 to the FK 4 system.

The constant of nutation and the system of astronomical constants

The author discusses the dependence of the constants of nutation and precession upon the values of other fundamental constants such as the dynamical ellipticity of the Earth, the mass of the Moon and the solar parallax in the case of two different theoretical models of the Earth.

Proper Motion of 3C273.

view Abstract Citations (2) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Proper Motion of 3C273. Jefferys, William H. Abstract The absolute proper motion of the radio source 3C273 has been determined from measurements on 14 plates covering the period 1887-1963. Two kinds of material were used to establish the proper motion system of the FK3. Eighty-two positions of 14 reference stars were obtained and corrections were applied to reduce them to the fundamental system; and statistical proper motions for 48 reference stars were calculated with the aid of material compiled by Vyssotsky and Williams (Publ. McCormick Obs. 10,1948). The material was formed into one set of normal equations and the solution of this system of equations effected by means of principles developed by Eichhorn (Astron. Nachr. 285, 233, 1960) and Jefferys (Astron. J. 68,111,1963). Since the FK3 uses Newcomb's constants of precession, the resulting FK3 proper motion must be corrected for the errors in Newcomb's constants. When this has been done, the absolute proper motion of the object, with its mean error, becomes ~= +0"0009+0'.'0025/yr, I a= -01.'0012~0'.'0025/yr. Therefore, the absolute proper motion of the object is zero within this rather small mean error, which constitutes strong evidence that the object is extragalactic. Publication: The Astronomical Journal Pub Date: March 1964 DOI: 10.1086/109243 Bibcode: 1964AJ.....69..142J full text sources ADS |

Determination of the Earth's Gravitational Potential from Observations on Sputnik 2 (1957β)

Summary R.A.E. observations of the rate of rotation of the orbital plane of Sputnik 2 are combined with Jeffreys's (1943, 1952) equations for the coefficients J and D in the spherical harmonic expansion of the Earth's gravitational field to give revised estimates of J and D. The relative uncertainties of the results emphasize the great value of satellite observations and the need for a revision of the spherical harmonic analysis of surface gravity. Comparison of the value of e−1 with that deduced from the constant of precession indicates that the Earth is not in a hydrostatic state.

The galactocentric circular velocity and corrections to the precession constant and the motion of the Equinox.

The galactocentric circular velocity and corrections to the precession constant and the motion of the Equinox.

An investigation of stellar motions: VI. The constants of galactic rotation and precession

An investigation of stellar motions: VI. The constants of galactic rotation and precession

An investigation of stellar motions: IV. The constants of solar motion, precession, and galactic rotation as derived from McCormick and Cape proper motions

An investigation of stellar motions: IV. The constants of solar motion, precession, and galactic rotation as derived from McCormick and Cape proper motions

Meridian Astronomy

ON February 10, Dr. H. Spencer Jones delivered his presidential address at the Royal Astronomical Society on “Meridian Astronomy”. He pointed out that the purpose of meridian astronomy is to provide a fundamental system of reference, and this is denned by the positions and proper-motions of a network of stars distributed with reasonable uniformity over the whole sky, together with the numerical value of the constant of precession. There are difficulties in the exact determination of the equator-the plane of reference—and also of the equinox-the zero point-because observations of the sun, which are used to fix these, are liable to personal errors of a systematic nature.

Note on Professor Newcomb's determination of the constant of precession and on the Paris Conference of 1896

Note on Professor Newcomb's determination of the constant of precession and on the Paris Conference of 1896

The Solar Parallax and its Related Constants

IT would be difficult to conceive a more masterly and comprehensive exposition of astronomical and physical constants than one just issued by Prof. W. Harkness, of the United States Naval Observatory. As is rightly pointed out, "The solar parallax is not an independent constant. On the contrary, it is entangled with the lunar parallax, the constants of precession and nutation, the parallactic inequality of the moon, the lunar inequality of the earth, the masses of the earth and moon, the ratio of the solar and lunar tides, the constant of aberration, the velocity of light, and the light equation.” It should therefore be determined simultaneously with all these quantities by means of a least-square adjustment, and Prof. Harkness develops such a method. The equations connecting the constants are given, whilst the numerical values which are discussed are based upon an enormous mass of astronomical, geodetic, gravitational, and tidal observations which have required more than two hundred years for their accumulation. The sources of probable error are also examined, and it is suggested how some of the constants may be improved in the future. The completeness of the lists. of constants, and the careful manner in which they are discussed and corrected by the comprehensive least-square adjustment which. is developed, justifies our giving seriatim the results obtained:—