scholarly journals Linking the FK5 to the ICRF

1998 ◽  
Vol 11 (1) ◽  
pp. 313-316
Author(s):  
F. Mignard ◽  
M. Froeschile
Keyword(s):  
Reference Frame ◽  
Proper Motion ◽  
Harmonic Functions ◽  
Optical Reference ◽  
Precessional Motion ◽  
Precession Constant

Abstract The Hipparcos optical reference frame is compared to the basic FK5 in order to determine the orientation at T0 = 1991.25 and the global spin between the two frames. The components of the spin are significant and suggest a correction the IAU76 value of the precession constant and to a possible non-precessional motion of the equinox of the FK5. The regional errors are analysed with harmonic functions and found to be as large as 150 mas in position and 3 mas/yr in proper motion.

scholarly journals Optical Reference Frame Defined by Carlsberg Meridian Catalogue La Palma Number 4

1990 ◽  
Vol 141 ◽  
pp. 391-401
Author(s):  
LV Morrison ◽  
RW Argyle ◽  
L Helmer ◽  
C Fabricius ◽  
OH Einicke ◽  
...  
Keyword(s):  
Reference Frame ◽  
Proper Motion ◽  
Reference Frames ◽  
Radio Sources ◽  
Present Epoch ◽  
Extragalactic Radio Sources ◽  
La Palma ◽  
Average Accuracy ◽  
Optical Reference

The contribution of the Carlsberg Meridian Catalogue La Palma Number 4 to the determination of the optical reference frame is discussed. This catalogue of almost 51000 stars provides one of the most accurate optical reference frames at the present epoch, having a density of 1 star per square degree, and an average accuracy of 0.″12 in position and 0.″003 per year in proper motion for stars with V<9. The catalogue also contains positions of reference stars with V>11 in the fields of benchmark extragalactic radio sources which can be used in linking the optical reference frame defined by the FK5 to the extragalactic frame.

scholarly journals Densifying the Optical Reference Frame: The Tycho-2 Catalog of 2.5 Million Stars

2000 ◽  
Vol 180 ◽  
pp. 75-79
Author(s):  
S.E. Urban ◽  
G.L. Wycoff
Keyword(s):  
Reference Frame ◽  
Proper Motion ◽  
Proper Motions ◽  
Naval Observatory ◽  
Optical Reference ◽  
The Mean ◽  
The U.S

AbstractSince the establishment of the Hipparcos Catalog as the defining source of the optical reference frame, densification beyond its ≈ 120,000 stars has been made possible by the utilization of the Tycho-1 Catalog. The ACT, combining the old Astrographic Catalog (AC) data with the Tycho-1 positions, is the best known example of this. The Tycho-2 consortium, led by E. Høg, has performed new reductions on the Tycho data. This not only has increased the astrometric and photometric accuracies of the original 1 million Tycho-1 stars, but also has added an additional 1.5 million stars. The U.S. Naval Observatory led the effort to compute the proper motions of these 2.5 million stars. They are based not only on the AC data but also include over 140 other ground-based catalogs, all directly reduced to the Hipparcos system. The result of these efforts is the Tycho-2 Catalog, available since February 2000. Positions, proper motions, and BT and VT magnitudes are given for 2.5 million stars. The catalog is 99% complete to V=11.0, and 90% complete to V=11.5. Positional accuracies at the mean epochs vary from < 10 mas for stars V < 9 to just under 100 mas for V > 12. Proper motion accuracies are estimated to be 1.3 mas/year to 3.0 mas/year for the same magnitude ranges. Photometric accuracies range from 0.02 magnitudes for the brightest stars to 0.25 magnitudes for the faintest.

scholarly journals The Extragalactic Radio/Optical Reference Frame

1991 ◽  
Vol 127 ◽  
pp. 123-129
Author(s):  
Kenneth J. Johnston ◽  
Jane L. Russell ◽  
Christian de Vegt ◽  
N. Zacharias ◽  
R. Hindsley ◽  
...  
Keyword(s):  
Reference Frame ◽  
Proper Motion ◽  
Reference Frames ◽  
Radio Sources ◽  
Radio Radiation ◽  
Emit Radiation ◽  
Optical Reference ◽  
The Galaxy ◽  
Optical Wavelengths ◽  
The Individual

The celestial positions of extragalactic radio sources may be determined to a precision of less than a milliarcsecond. Further, since these sources are believed to be at great distances from the galaxy, little or no proper motion is expected on scales of order a milliarcsecond. Therefore a reference frame based on the positions of carefully selected sources so that display compact radiation on scales less than a milliarcsecond will noticeably improve the precision of present celestial reference frames. If the radio objects making up the reference frame also emit radiation at optical wavelengths, and assuming the optical/radio radiation is coincident, the radio frame can update the optical frame to the accuracy of the individual optical positions.

scholarly journals Progress Report on the Southern Proper Motion Program

1995 ◽  
Vol 166 ◽  
pp. 357-357
Author(s):  
I. Platais ◽  
T. M. Girard ◽  
V. Kozhurina-Platais ◽  
R. A. Mendez ◽  
W. F. Van Altena ◽  
...  
Keyword(s):  
Reference Frame ◽  
Proper Motion ◽  
Systematic Errors ◽  
Progress Report ◽  
Model Choice ◽  
Plate Model ◽  
Field Independent ◽  
The Status ◽  
First Results ◽  
Galaxy Model

We present the status of the Yale/San Juan Southern Proper Motion program (SPM) which is the southern hemisphere extension of the Lick Observatory Northern Proper Motion program with respect to faint galaxies (Platais et al., 1993). To date, measurements and reductions in the South Galactic Pole region comprising ≈ 1000 square-degrees on the sky have been finished. At this stage of the SPM program particular attention has been paid to the plate model choice along with an assessment of and accounting for systematic errors. For our establishing of a secondary reference frame we have noticed the presence of a potentially dangerous effect, so–called field–independent coma which is caused by lens decentering. We acknowledge the superb Hipparcos preliminary positions without which such analysis would be virtually impossible. The SPM data at the SGP region have also been used to constrain a multi–component Galaxy model. First results of this analysis are presented.

scholarly journals Interrelation of Present Optical and Radio Reference Frames

1984 ◽  
Vol 110 ◽  
pp. 357-360
Author(s):  
Chr. de Vegt
Keyword(s):  
Reference Frame ◽  
Northern Hemisphere ◽  
Reference Frames ◽  
Systematic Errors ◽  
Future Developments ◽  
Optical Reference

Comparison of optical and radio positions in the northern hemisphere yields local systematic differences up to 0″.2, mainly due to combined systematic errors of current optical reference frame and contributing main catalogues. Interrelations of radio/optical frame and future developments are discussed.

scholarly journals Contributions of the USNO to the Optical Reference Frame

1997 ◽  
Vol 165 ◽  
pp. 453-462
Author(s):  
Thomas Corbin
Keyword(s):  
Reference Frame ◽  
Reverse Order ◽  
Good Working ◽  
Working Definition ◽  
Optical Reference ◽  
Definition Of ◽  
Celestial Sphere ◽  
Celestial Reference Frame ◽  
Frame Rigidity ◽  
Zero Points

A good, working definition of what is required in a celestial reference frame is that it must provide observable fiducial points on the Celestial Sphere with internally consistent positions that are referred to coordinate axes of known direction. In reality, this statement gives the goals in the reverse order from that in which each must be achieved, the definition of the axes, or zero points of the system give orientation to the observationally defined set of primary objects whose coordinate relation to each other must give the frame rigidity. Finally, the primary objects are generally too sparse to define the frame within areas of less than tens of square degrees, and so additional objects must be related to the frame to increase the density. This last step is required to make the frame useful for most observational applications.

scholarly journals Proper Motions With Respect to the Extragalactic Reference Frame

1990 ◽  
Vol 141 ◽  
pp. 407-417
Author(s):  
A. R. Klemola
Keyword(s):  
Reference Frame ◽  
Proper Motion ◽  
Milky Way ◽  
Proper Motions ◽  
Stellar Proper Motions

The Lick proper motion program, one of several using galaxies as a reference frame, is summarized with a statement of work accomplished for the non-Milky Way sky. The problem of identifying relatively transparent regions at low galactic latitudes is discussed, with tabular results presented for 41 windows from the literature having observable galaxies. These fields may be helpful for attaching stellar proper motions directly to the extragalactic frame.

scholarly journals The Possibility to Link Radio and Optical Reference Frames With Artificial Satellites

1990 ◽  
Vol 141 ◽  
pp. 194-194
Author(s):  
Tong Fu
Keyword(s):  
Reference Frame ◽  
Reference Frames ◽  
Artificial Satellites ◽  
Radio Sources ◽  
Bl Lac Objects ◽  
Extragalactic Radio Sources ◽  
Bl Lac ◽  
Optical Reference ◽  
Radio Stars ◽  
Fundamental Reference

Based on extragalactic radio sources, a new high precision extragalactic radio reference frame can be established from radio interferometric measurements. To link the optical fundamental reference frame presently represented by the FK4/5 to the extragalactic radio frame, the optical counterparts of extragalactic radio sources (quasars, BL Lac objects etc.) and radio stars are the most important classes of objects. Besides these two classes of objects, are there any other objects which can be used to link the optical and radio frames? A posible answer is that artificial satellites could be a candidate class of objects contributing to this subject.

A radio optical reference frame. II - Additional radio and optical source positions in the Northern Hemisphere

1991 ◽  
Vol 101 ◽  
pp. 2266 ◽  
Author(s):  
J. L. Russell ◽  
K. J. Johnston ◽  
C. Ma ◽  
D. Shaffer ◽  
C. de Vegt
Keyword(s):  
Reference Frame ◽  
Northern Hemisphere ◽  
Optical Source ◽  
Optical Reference

scholarly journals RORF - A Radio Optical Reference Frame

1995 ◽  
Vol 166 ◽  
pp. 381-381
Author(s):  
N. Zacharias ◽  
A.L. Fey ◽  
J.L. Russell ◽  
K.J. Johnston
Keyword(s):  
Reference Frame ◽  
Group Delay ◽  
Phase Delay ◽  
Dual Frequency ◽  
Radio Observations ◽  
Optical Reference ◽  
Vlbi Data

The radio observations are based on more than one million pairs of group delay and phase delay rate observations from all applicable dual frequency Mark–III VLBI data from 1979 until the end of 1993.

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