A Study of the Accuracy of Narrow Field Astrometry using Star Trails taken with the CFHT

Han, Inwoo; Gatewood, George

doi:10.1086/133564

Cited by 11 publications

(11 citation statements)

References 9 publications

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“…For differential astrometry, previous investigations have dealt with angular separation measures. The effect is found to be at the 1-2 mas level for arcminute separations and several minutes integration time (Han and Gatewood 1995), e.g. applicable to double star and parallax observations.…”

Section: Introductionmentioning

confidence: 80%

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Measuring the Atmospheric Influence on Differential Astrometry: A Simple Method Applied to Wide Field CCD Frames

Zacharias¹

1996

PASP

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Sets of short exposure, guided CCD frames are used to measure the noise added by the atmosphere to differential astrometric observations. Large nightly variations that are correlated with the seeing have been found in the data obtained over 2 years at the KPNO and CTIO 0.9-meter telescopes. The rms noise added by the atmosphere, after a linear transformation of the raw x, y data, is found to be 3 to 7 mas, normalized to 100 seconds exposure time and a field of view of 20 arcminutes near the zenith. An additional nearly constant noise (base-level) of 8.5 mas = 0.012 pixel is found for the KPNO and 6.0 mas = 0.015 pixel for the CTIO telescope. This implies that a ground-based, all sky, astrometric survey from guided CCD frames is more likely limited by the base-level noise than by the atmosphere and could reach an accuracy better than 10 mas under good seeing conditions.

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Section: Introductionmentioning

confidence: 80%

“…Semi-empirical and empirical results have been published previously, e.g. (Lindegren 1980;Kleine 1983;Han 1989;Monet andMonet 1992, Han andGatewood 1995). This effect ultimately limits the accuracy of ground-based astrometric observations, and it is important to find these limits.…”

Section: Introductionmentioning

confidence: 95%

Measuring the Atmospheric Influence on Differential Astrometry: A Simple Method Applied to Wide Field CCD Frames

Zacharias¹

1996

PASP

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“…Ground-based astrometric measurements are limited by atmospheric turbulence (Han & Gatewood 1995). The typical rms size of this random effect depends on the seeing, the separation between objects (θ), and the exposure time (T ) as follows (Bouy et al 2013):…”

Section: Errorsmentioning

confidence: 99%

The VMC survey

Cioni

Bekki

Girardi

et al. 2016

A&A

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Aims. In this study we use multi-epoch near-infrared observations from the VISTA survey of the Magellanic Cloud system (VMC) to measure the proper motions of different stellar populations in a tile of 1.5 deg 2 in size in the direction of the Galactic globular cluster 47 Tuc. We obtain the proper motion of the cluster itself, of the Small Magellanic Cloud (SMC), and of the field Milky Way stars. Methods. Stars of the three main stellar components are selected according to their spatial distributions and their distributions in colour−magnitude diagrams. Their average coordinate displacement is computed from the difference between multiple K s -band observations for stars as faint as K s = 19 mag. Proper motions are derived from the slope of the best-fitting line among ten VMC epochs over a time baseline of ∼1 yr. Background galaxies are used to calibrate the absolute astrometric reference frame. Results. The resulting absolute proper motion of 47 Tuc is (μ α cos(δ), μ δ ) = (+7.26 ± 0.03, −1.25 ± 0.03) mas yr −1 . This measurement refers to about 35 000 sources distributed between 10 and 60 from the cluster centre. For the SMC we obtain (μ α cos(δ), μ δ ) = (+1.16 ± 0.07, −0.81 ± 0.07) mas yr −1 from about 5250 red clump and red giant branch stars. The absolute proper motion of the Milky Way population in the line of sight (l = 305.9, b = −44.9) of this VISTA tile is (μ α cos(δ), μ δ ) = (+10.22 ± 0.14, −1.27 ± 0.12) mas yr −1 and has been calculated from about 4000 sources. Systematic uncertainties associated with the astrometric reference system are 0.18 mas yr −1 . Thanks to the proper motion we detect 47 Tuc stars beyond its tidal radius.

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“…The proper motions of SMC, 47 Tuc, and MW stars, discussed in this paper, were corrected for it by subtracting from their respective proper motions that of the galaxies. Ground-based astrometric measurements are limited by atmospheric turbulence (Han & Gatewood 1995). The typical rms size of this random effect depends on the seeing, the separation between objects (θ), and the exposure time (T ) as follows (Bouy et al 2013):…”

Section: Errorsmentioning

confidence: 99%

The VMC survey - XVII. The proper motion of the Small Magellanic Cloud and of the Milky Way globular cluster 47 Tucanae

Cioni,

Bekki,

Girardi

et al. 2015

Preprint

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Aims. In this study we use multi-epoch near-infrared observations from the VISTA survey of the Magellanic Cloud system (VMC) to measure the proper motion of different stellar populations in a tile of 1.5 deg 2 in size in the direction of the Galactic globular cluster 47 Tuc. We obtain the proper motion of the cluster itself, of the Small Magellanic Cloud (SMC), and of the field Milky Way stars. Methods. Stars of the three main stellar components are selected from their spatial distribution and their distribution in colourmagnitude diagrams. Their average coordinate displacement is computed from the difference between multiple K s -band observations for stars as faint as K s = 19 mag. Proper motions are derived from the slope of the best-fitting line among 10 VMC epochs over a time baseline of ∼ 1 yr. Background galaxies are used to calibrate the absolute astrometric reference frame. Results. The resulting absolute proper motion of 47 Tuc is (µ α cos(δ), µ δ ) = (+7.26 ± 0.03, −1.25 ± 0.03) mas yr −1 . This measurement refers to about 35000 sources distributed between 10 ′ and 60 ′ from the cluster centre. For the SMC we obtain (µ α cos(δ), µ δ ) = (+1.16 ± 0.07, −0.81 ± 0.07) mas yr −1 from about 5250 red clump and red giant branch stars. The absolute proper motion of the Milky Way population in the line-of-sight (l = 305.9, b = −44.9) of this VISTA tile is (µ α cos(δ), µ δ ) = (+10.22 ± 0.14, −1.27 ± 0.12) mas yr −1 and results from about 4000 sources. Systematic uncertainties associated to the astrometric reference system are 0.18 mas yr −1 . Thanks to the proper motion we detect 47 Tuc stars beyond its tidal radius.

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A Study of the Accuracy of Narrow Field Astrometry using Star Trails taken with the CFHT

Cited by 11 publications

References 9 publications

Measuring the Atmospheric Influence on Differential Astrometry: A Simple Method Applied to Wide Field CCD Frames

Measuring the Atmospheric Influence on Differential Astrometry: A Simple Method Applied to Wide Field CCD Frames

The VMC survey

The VMC survey - XVII. The proper motion of the Small Magellanic Cloud and of the Milky Way globular cluster 47 Tucanae

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