ABSTRACT submitted to the Annual Meeting of the AAS Division on Dynamical Astronomy, Cannes, France, April 19-23, 2004

The Allegheny Observatory CCD Parallax Program

G. Gatewood, Allegheny Observatory, University of Pittsburgh, 15214

gatewood@pitt.edu, website http://www.pitt.edu/~aobsvtry .

To extend our bright star parallax program to below the magnitude cutoff of the HIPPARCOS catalog, we have installed a CCD tail piece on the red-light correct 0.76-m Thaw refractor. The 2048 x 2048 back-side-illuminated Marconi chip has a scale of 0.196 arcs sec per pixel on the f18.7 refractor.  Initial estimates of the precision of the system as a function of stellar magnitude have been obtained from the standard error of the positions of stars observed for four hours, the approximate observing time given to a parallax target star.  As illustrated by the HIPPARCOS catalog, a parallax study extending over approximately 3 years has similar positional and parallax standard errors.  Our tests indicate that the standard error is between approximately 0.6 and 1 mas down to stars as faint as the 16^th magnitude.  The results are better illustrated under research on our website.  Stars included on the CCD program are also listed there as are photographs of the interior of the tail piece.

Most of the program stars are either suspected late M dwarfs, or cool white dwarfs apparently within 20 parsecs of the Sun.  U, B, V, R, and I, photometry of the target and reference stars is obtained with a secondary telescope and CCD camera attached to the refractor.  Correction to absolute will be enhanced by the use of relatively faint reference stars for which we will have approximate temperatures and magnitudes. Bright stars are observed through central ND filters of 2.5, 5.0, 7.5, and 10.0 magnitudes. A similar precision is obtained for ND filtered and non-ND filtered stars.  This research and  instrumentation was made possible by National Science Foundation grants 0098552 and 013822.