scholarly journals 24. Commission des Parallaxes Stellaires et des Mouvements Propres

1936 ◽  
Vol 5 ◽  
pp. 144-155
Author(s):  
M. S. A. Mitchell ◽  
MM. Adams ◽  
Alden ◽  
Bianchi ◽  
Cecchini ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Systematic Errors ◽  
Probable Error ◽  
Proper Motions ◽  
Astrophysical Journal ◽  
Trigonometric Parallaxes ◽  
Substantial Progress

In November 1934 the President circulated a letter to the members of the Commission as follows:Since the 1932 meeting the following projects have been completed, or are nearing completion:(1)The publication of many lists of trigonometric parallaxes.(2)The determination of the spectroscopic parallaxes of 4179 stars at Mt Wilson Observatory by Adams, Joy and Humason.(3)A discussion of systematic errors of trigonometric parallaxes by van Maanen and a re-discussion in the Astrophysical Journal of the same material by Mitchell and by Sterne.(4)The compilation of a second Yale Catalogue to include parallaxes completed before the end of 1934.(5)Substantial progress on the proper motions of 32,000 stars by Boss and his associates at the Dudley Observatory.(6)The publication at the Radcliffe Observatory of the proper motions of 32,000 stars from photographs on 115 Selected Areas.(7)The completion of the dynamical parallaxes of 2000 stars.(8)The completion of the proper motions of 18,000 stars derived from parallax plates at the Leander McCormick Observatory.(9)The publication at the Yale Observatory of the proper motions of 40,000 stars with a probable error less than 0”.010 determined from photographs by re-observing in zones the Astronomische Gesellschaft stars.(10)The determination of the proper motions of 50,000 stars in the Southern Hemisphere by Luyten from Harvard photographs.

Statistics and parallaxes

1978 ◽  
Vol 48 ◽  
pp. 7-29
Author(s):  
T. E. Lutz
Keyword(s):  
Experimental Design ◽  
Statistical Methods ◽  
Review Paper ◽  
Systematic Errors ◽  
Past Experience ◽  
Random Errors ◽  
Trigonometric Parallaxes ◽  
Systematic And Random Errors

This review paper deals with the use of statistical methods to evaluate systematic and random errors associated with trigonometric parallaxes. First, systematic errors which arise when using trigonometric parallaxes to calibrate luminosity systems are discussed. Next, determination of the external errors of parallax measurement are reviewed. Observatory corrections are discussed. Schilt’s point, that as the causes of these systematic differences between observatories are not known the computed corrections can not be applied appropriately, is emphasized. However, modern parallax work is sufficiently accurate that it is necessary to determine observatory corrections if full use is to be made of the potential precision of the data. To this end, it is suggested that a prior experimental design is required. Past experience has shown that accidental overlap of observing programs will not suffice to determine observatory corrections which are meaningful.

scholarly journals CPC2 Reduction with Hipparcos and Proper Motions in The Southern Hemisphere

1998 ◽  
Vol 11 (1) ◽  
pp. 551-551
Author(s):  
N. Zacharias ◽  
M.I. Zacharias ◽  
C. de Vegt ◽  
C.A. Murray
Keyword(s):  
Southern Hemisphere ◽  
Systematic Errors ◽  
Reference Star ◽  
Proper Motions ◽  
Positional Accuracy ◽  
Star Catalog ◽  
Naval Observatory ◽  
Celestial Reference System ◽  
First Time ◽  
Better Than

The Second Cape Photographic Catalog (CPC2) contains 276,131 stars covering the entire Southern Hemisphere in a 4-fold overlap pattern. Its mean epoch is 1968, which makes it a key catalog for proper motions. A new reduction of the 5687 plates using on average 40 Hipparcos stars per plate has resulted in a vastly improved catalog with a positional accuracy of about 40 mas (median value) per coordinate, which comes very close to the measuring precision. In particular, for the first time systematic errors depending on magnitude and color can be solved unambiguously and have been removed from the catalog. In combination with the Tycho Catalogue (mean epoch 1991.25) and the upcoming U.S. Naval Observatory CCD Astrograph Catalog (UCAC) project proper motions better than 2 mas/yr can be obtained. This will lead to a vastly improved reference star catalog in the Southern Hemisphere for the final Astrographic Catalogue (AC) reductions, which will then provide propermotions for millions of stars when combined with new epoch data. These data then will allow an uncompromised reduction of the southern Schmidt surveys on the International Celestial Reference System (ICRS).

scholarly journals Commission 24. (Stellar Parallaxes and Proper Motions.)

1933 ◽  
Vol 4 ◽  
pp. 246-247
Author(s):  
S. A. Mitchell ◽  
F. Slocum
Keyword(s):  
Systematic Errors ◽  
Proper Motions ◽  
Fundamental Assumption ◽  
Trigonometric Parallaxes ◽  
Informal Discussion ◽  
Right Ascension

There were two meetings of the Commission. The first meeting was devoted to an informal discussion of programmes for parallax work. The second session was devoted to a discussion of systematic errors. The President gave a brief summary of the two latest determinations of the systematic errors of trigonometric parallaxes, by Schlesinger (parallaxes published to 1924) and by van Maanen (parallaxes to 1927). Both investigators had used the same basis of comparison, namely, the Mt Wilson spectroscopic parallaxes, and both had made the same fundamental assumption, namely, that the systematic errors of the spectroscopic parallaxes depending on right ascension were negligible.

scholarly journals Proper Motions of OB Stars in Both Hemispheres

1974 ◽  
Vol 61 ◽  
pp. 227-227
Author(s):  
Haruo Yasuda
Keyword(s):  
Southern Hemisphere ◽  
Fundamental System ◽  
Systematic Errors ◽  
Radial Velocities ◽  
Distance Scale ◽  
Proper Motions ◽  
Stellar Kinematics ◽  
Ob Stars

From a comparison between the rotational velocities derived from radial velocities and space motions of OB stars, large systematic errors of FK4 proper motions in the southern hemisphere are evaluated; these may be expected, from the known accuracy of the FK4. The error of adopted distance scale is also examined. It is suggested that meridian observations of OB stars should be extended to the southern hemisphere to further researches, not only on stellar kinematics, but also on the fundamental system.

scholarly journals A Determination of Secular Parallaxes of Reference Stars from Relative Proper Motions of Open Clusters

1970 ◽  
Vol 7 ◽  
pp. 74-76
Author(s):  
A. N. Deutsch
Keyword(s):  
Systematic Errors ◽  
Open Clusters ◽  
Radial Velocities ◽  
Proper Motions ◽  
The Mean

The determination of secular parallaxes of stars is usually based on meridian observations of proper motions of bright stars, this introducing known systematic errors. The mean parallaxes of stars can be obtained by means of radial velocities which are known for the bright stars. The more perspective method, the reference of stars to galaxies, is not applicable at low galactic latitudes.

scholarly journals Absolute Magnitudes from Trigonometric and Statistical Parallaxes

1973 ◽  
Vol 54 ◽  
pp. 3-10
Author(s):  
P. Van De Kamp
Keyword(s):  
Systematic Errors ◽  
Probable Error ◽  
Trigonometric Parallaxes ◽  
Absolute Magnitudes

The attainable accuracy of photographic trigonometric parallaxes may be improved by the use of modern measuring engines, larger number of exposures, facilitated by increased speed of emulsions, more refined knowledge of reduction to absolute parallax. Systematic errors remain an obstacle both in trigonometric and statistical parallaxes.With an attainable goal of ±0″.002 for the probable error of a parallax it appears difficult to obtain absolute magnitudes with a probable error less than 0.2 mag. for stars beyond 20 pc.

scholarly journals 8. Commission de l’Astronomie Méridienne

1933 ◽  
Vol 4 ◽  
pp. 28-31
Author(s):  
Frank Dyson ◽  
MM. Aiginitis ◽  
Armellini ◽  
Bemporad ◽  
Boss ◽  
...  
Keyword(s):  
Milky Way ◽  
Systematic Errors ◽  
Special Importance ◽  
Proper Motions ◽  
International Astronomical Union ◽  
Systematic Correction ◽  
International Astronomical ◽  
Right Ascension

Since the last meeting of the International Astronomical Union, much attention has been given both in Germany and America to the systematic errors of the fundamental catalogues of Boss and Auwers. This is of special importance if the proper motions of any of the stars are to be used in the verification of the rotation in the plane of the Milky Way. The periodic errors in the proper motions, both in right ascension and declination, are of significance in this connection, while the motion of the equinox is required for the determination of precession, and the systematic correction to the proper motions of declination affects the position of the Solar Apex and the Vertices of the Star Streams.

scholarly journals Preliminary Results of the Determination of Absolute Proper Motions of Stars Referred to Galaxies

1968 ◽  
Vol 1 ◽  
pp. 297-300
Author(s):  
N.V. Fatčihin
Keyword(s):  
Proper Motion ◽  
Focal Length ◽  
Probable Error ◽  
Proper Motions ◽  
Average Quality ◽  
Preliminary Results ◽  
Measuring Machine

Absolute proper motions have been determined for 14000 stars in the 82 areas indicated in Figure 1. These proper motions result from measures made on 105 plate pairs taken with the Pulkovo normal astrograph which has a focal length of 3·5 m. The plates, which had an average epoch difference of 22·4 years, were measured film-to-film in a Repsold measuring machine. The number of galaxies used for defining zero proper motion was 271, and among the stars measured were 1283 from the AGK3. The probable error of a determination of proper motion from one plate pair wasThe images of the galaxies were estimated as having an average quality of 6 on a scale of 10. (Deutsch et al., 1955).

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

Systematic errors in equilibrium composition of ternary liquid-liquid systems and their effect on the calculated number of theoretical stages of countercurrent extraction

1988 ◽  
Vol 53 (6) ◽  
pp. 1172-1180
Author(s):  
Ján Dojčanský ◽  
Soňa Bafrncová ◽  
Július Surový
Keyword(s):  
Equilibrium Composition ◽  
Systematic Errors ◽  
Liquid Equilibrium ◽  
Countercurrent Extraction ◽  
Liquid Systems ◽  
Equilibrium Concentrations ◽  
Line Slope ◽  
Tie Line ◽  
Calculated Number

The influence of magnitude of systematic errors in the determination of ternary liquid-liquid equilibrium concentrations on the accuracy of the calculated number of theoretical stages of countercurrent extraction is evaluated on using five hypothetical systems differing in the extent of mutual solubility of components, tie-line slope, and type of binodal curve.

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