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 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 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).

John Tebbutt’s Observations of Halley’s Comet in 1910

1986 ◽  
Vol 6 (3) ◽  
pp. 354-358 ◽  
Author(s):  
Siegfried Röser ◽  
Graeme L. White
Keyword(s):  
Detailed Analysis ◽  
Systematic Errors ◽  
Astronomical Society ◽  
Royal Astronomical Society ◽  
Amateur Astronomer ◽  
Halley's Comet ◽  
Right Ascension ◽  
Rms Errors

AbstractThe Windsor amateur astronomer, John Tebbutt, had a ceased observing in 1907. However, in 1909, at the age of 75, he came out of retirement to observe Halley’s comet and his astrometric positions were published in the Monthly Notices of the Royal Astronomical Society. These data were used, together with most published observations from the 1835 and 1910 apparitions, for the computation of Halley’s orbit for ESA’s Halley intercept spacecraft, Giotto. A detailed analysis of the observations have shown minor imperfections that, when corrected, gave rms errors of 3''.5 arc in right ascension and 2''.8 in declination. His systematic errors are negligible at the 0''.2 level.

scholarly journals Astrometry With Schmidt Telescopes

1984 ◽  
Vol 78 ◽  
pp. 217-224
Author(s):  
C A Murray
Keyword(s):  
Reference Frame ◽  
Proper Motions ◽  
Large Area ◽  
Full Field ◽  
Potential Value ◽  
Focal Surface ◽  
Single Plate ◽  
Trigonometric Parallaxes ◽  
The Absolute

Photographic astrometry, including work with Schmidt telescopes, can be divided into two main fields, (i) the measurement of positions of objects relative to a reference frame of stars with known celestial coordinates, and (ii) the measurement of relative proper motions and trigonometric parallaxes from a series of plates taken on the same field. The former demands a knowledge of the absolute transformation between angles on the sky and measurements on a plate, whereas in the latter we are only interested in differential transformations from plate to plate. The potential value of Schmidt telescopes for both these fields of astrometry lies in the large area of sky and range of magnitude which can be imaged on a single plate. The former advantage is however, to some extent offset by the curvature of the focal surface which means that, in order to utilize the full field the plates must be constrained to the form of the focal surface during exposure.

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 NPC, A New Combined Position Catalogue of Stars in the Northern Pole Region

1997 ◽  
Vol 165 ◽  
pp. 499-504
Author(s):  
L.G. Taff ◽  
V.V. Tel’nyuk-Adamchuk ◽  
O.A. Molotaj
Keyword(s):  
Main Task ◽  
Proper Motions ◽  
Polar Cap ◽  
Position Errors ◽  
The North ◽  
The Mean ◽  
North Polar ◽  
Right Ascension ◽  
Second Use ◽  
Rms Errors

AbstractThe main task of this work was to construct a new catalogue of positions and proper motions of stars in the north polar cap, and using the results obtained to study the systematic features of the source catalogues as well as the reference system in the polar region. To achieve the goal, thirteen source catalogues, both meridian and photographic, covering an epoch span near one and a half century, were collected. Most of them were not involved in the process of both the PPM and the ACRS constructions. The new combined catalogue of positions and proper motions, named North Polar Catalogue (NPC), lists 4272 stars on the FK5 system, J2000.0. The catalogue was constructed using the method of infinitely overlapping circles. It represents the second use of this procedure to construct a star catalogue. External rms accuracy of positions for the epoch of 2000 is equal to 015 and 025 for the centennial proper motions, respectively. The internal rms errors of positions at the mean catalogue epoch, near 1940, are equal to 018 and 015 for right ascension and declination correspondingly, while external rms position errors for that epoch are of the order of 005. Comparisons were made between the NPC and three modern catalogues, the FK5, PPM, and ACRS. The systematic differences between the new catalogue and PPM one for the epoch of 2000 are valuable, especially in the case of errors depending on right ascension. The authors consider as an essential part of the systematic differences that, which is caused by some shortcomings of the PPM in the polar zone. For the mean epoch of the new catalogue positions the systematic differences are smaller.

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