We present a demonstration of a technique that can significantly improve the absolute astrometric accuracy of HST data from its current levels of uncertainty (1-2” or worse) to an accuracy in the range about 0.1-0.3”, thus representing about an order of magnitude improvement. For the first time, the absolute astrometric accuracy of HST data can thus begin to approach the exquisite 0.1” resolution of the telescope. The procedure described here involves creating catalogs of HST images, then comparing the resulting catalogs with the recently completed Guide Star Catalog 2 (GSC2), and using the cross-comparison to calculate the offsets in the astrometric header information of the image. This initial demonstration is carried out on a total of 834 science exposures that are contained in 152 different ACS/WFC associations, which are all public GO data obtained during the first year of ACS operations. With a modest amount of additional effort, this technique can be extended to single images (which generally have more cosmic rays) as well as subsets of the data from other HST instruments (WFPC2, STIS, NICMOS) that have sufficient GSC2 sources in the field. The result is a significant improvement in the scientific quality, hence the discovery potential, of HST images.

Astrometry

Header

Field of view

Source

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Citations (3)

VizieR Online Data Catalog: Positions of high-redshift luminous quasars (Schneider+ 1992)

yCat (1994)

Donald P. Schneider John N. Bahcall David H. Saxe Neta A. Bahcall R. Doxsey

Source

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Accurate positions and finding charts for 528 high-redshift, luminous quasars

Publications of the Astronomical Society of the Pacific (1992)

Donald P. Schneider John N. Bahcall David H. Saxe Neta A. Bahcall R. Doxsey

We present finding charts and J2000 positions accurate to 1" for the 528 high-redshift (z > 1), luminous (MV < -25.5) quasars investigated in the Hubble Space Telescope Snapshot Survey. The information was produced with the Space Telescope Science Institute's Astrometric Support Program.

Snapshot (computer storage)

Spitzer Space Telescope

Observational cosmology

Photometric redshift

10.1086/133037

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Citations (10)