Issue |
A&A
Volume 427, Number 3, December I 2004
|
|
---|---|---|
Page(s) | 1127 - 1143 | |
Section | Celestial mechanics and astrometry | |
DOI | https://doi.org/10.1051/0004-6361:20041481 | |
Published online | 16 November 2004 |
Filtration of atmospheric noise in narrow-field astrometry with very large telescopes
Main Astronomical Observatory, National Academy of Sciencies of the Ukraine, Zabolotnogo 27, 03680 Kyiv-127, Ukraine e-mail: laz@mao.kiev.ua
Received:
17
June
2004
Accepted:
19
July
2004
This paper presents a non-classic approach to
narrow field astrometry that offers a significant improvement over
conventional techniques due to enhanced
reduction of atmospheric image motion.
The method is based on two key elements: apodization of the
entrance pupil and the enhanced virtual symmetry of reference stars.
Symmetrization is implemented by setting special weights
to each reference star. Thus a reference field itself forms a virtual
net filter that effectively attenuates the image motion spectrum.
Atmospheric positional error was found to follow
a power dependency on angular
field size R and aperture D; here k is some optional even
integer
limited by a number N of
reference stars, and
is a term dependent on k and
the magnitude and sky star distribution in the field.
As compared to conventional techniques for which
, the improvement
in accuracy increases by some orders.
Limitations to astrometric performance of monopupil
large ground-based telescopes are estimated. The total
atmospheric and photon noise for
at a 10 m telescope at good
seeing was found to be,
depending on sky star density,
10 to 60 μas per 10 min exposure in R band. For a 100 m telescope
and FWHM =
(low-order adaptive optics corrections) the potential
accuracy is 0.2 to 2 μas.
Key words: atmospheric effects / turbulence / methods: data analysis / astrometry / instrumentation: high angular resolution
© ESO, 2004
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