A Caltech Library Service

Precision Astrometry With Adaptive Optics

Cameron, P. B. and Britton, M. C. and Kulkarni, S. R. (2009) Precision Astrometry With Adaptive Optics. Astronomical Journal, 137 (1). pp. 83-93. ISSN 0004-6256. doi:10.1088/0004-6256/137/1/83.

PDF - Published Version
See Usage Policy.


Use this Persistent URL to link to this item:


We investigate the limits of ground-based astrometry with adaptive optics using the core of the Galactic globular cluster M5. Adaptive optics systems provide near diffraction-limit imaging with the world's largest telescopes. The substantial improvement in both resolution and signal-to-noise ratio enables high-precision astrometry from the ground. We describe the dominant systematic errors that typically limit ground-based differential astrometry, and enumerate observational considerations for mitigating their effects. After implementing these measures, we find that the dominant limitation on astrometric performance in this experiment is caused by tilt anisoplanatism. We then present an optimal estimation technique for measuring the position of one star relative to a grid of reference stars in the face of this correlated random noise source. Our methodology has the advantage of reducing the astrometric errors to ~1/√t and faster than the square root of the number of reference stars, effectively eliminating noise caused by atmospheric tilt to the point that astrometric performance is limited by centering accuracy. Using 50 reference stars, we demonstrate a single-epoch astrometric precision of ≈1 mas in 1 s, decreasing to ≾ 100 μas in 2 minutes of integration time at the Hale 200 inch telescope. We also show that our astrometry is accurate to ≾ 100 μas for observations separated by 2 months. Finally, we discuss the limits and potential of differential astrometry with current and next-generation large-aperture telescopes. At this level of accuracy, numerous astrometric applications become accessible, including planet detection, astrometric microlensing signatures, and kinematics of distant Galactic stellar populations.

Item Type:Article
Related URLs:
URLURL TypeDescription
Kulkarni, S. R.0000-0001-5390-8563
Additional Information:© 2009. The American Astronomical Society. Received 2008 May 13; accepted 2008 September 16; published 2008 December 10. Print publication: Issue 1 (2009 January). We thank N. Law, M. Ireland, D. Le Mignant, A. Kraus, M. van Kerkwijk, and A. Gould for useful discussions on astrometry. We also thank Palomar Observatory for providing support for the DIMM/MASS unit used in this study. This work has been supported by NASA, and by the National Science Foundation Science and Technology Center for Adaptive Optics, managed by the University of California at Santa Cruz under cooperative agreement no. AST-9876783. Facilities: Hale (PALAO/PHARO).
Funding AgencyGrant Number
Subject Keywords:astrometry; globular clusters: individual (M5); instrumentation: adaptive optics; methods: statistical
Issue or Number:1
Record Number:CaltechAUTHORS:CAMaj09
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:12821
Deposited By: Archive Administrator
Deposited On:25 Dec 2008 01:03
Last Modified:08 Nov 2021 22:33

Repository Staff Only: item control page