DIVISION I / COMMISSION 8 / WORKING GROUP ASTROGRAPHIC CATALOGUE AND CARTE DU CIEL PLATES

BEATRICE BUCCIARELLI; ALAIN FRESNAU; CARLOS ABAD; ROBERT W. ARGYLE; JAMES BIGGS; NOAH BROSCH; GEORGE V. COYNE; EMMANUAEL DAVOUST; JEAN-PIERRE M. DE CUYPER; EDWIN L. VAN DESSEL; CHRISTINE DUCOURANT; IVAN H. BUSTOS FIERRO; MICHAEL GEFFERT; ELENA V. GLUSHKOVA; MICHAEL J. IRWIN; DAYTON L. JONES; KARI A. LUMME; J. L. MUI?NOS; MICHAEL ODENKIRCHEN; ROSA B. ORELLANA; THIERRY PAUWELS; THEODORE J. RAFFERTY; M. SANCHEZ; J¨ORG SANNER; MILCHO K. TSVETKOV; ALAN E. VAUGHAN

Transactions IAU

Cambridge Journals

Lugar: Cambridge; Año: 2008 vol. 3 p. 95 - 97

1743-9213

Various experiments have definitely demonstrated that one-micron accuracy (0.06) on thedefinition of stellar images on CdC plates cannot be claimed, as it was speculated back in 1999.More realistically, a 2-3 micron accuracy is achievable, getting worse toward the survey magnitudelimit, with an average magnitude error of 0.3. The level of astrometric accuracy correspondsto a 0.2 - 0.3 error in position at Epoch 1900, which, once used as first Epoch for proper motiondetermination in combination with modern epoch observations, can produce errors at thelevel of 2-5 mas/yr, thereby allowing to detect stellar motions larger than 0.01/yr, which at adistance of 500 pc from the Sun correspond to ∼25-60 km/s tangential velocity. Therefore, theAC/CdC heritage collection can be regarded as a highly valuable first-epoch material, e.g., forthe realization of a Tycho-2 extension to fainter magnitudes (∼15 photographic), especially inselected areas where radial velocity data are available, for the exploration of stellar kinematicsbeyond our solar neighborhood.In the following I present a possibly non-exhaustive list of efforts that, since the last IAUin Prague, have been undertaken to digitize parts of the AC/CdC collections pertaining to thedifferent zones, with the twofold intent of exploiting the scientific potential of these plates andmaking the digitized images available to the community.The Cart du Ciel plate material deserves to be salvaged and digitally recorded to the bestaccuracy for those astrophysical investigations which can exploit this unique, 100 year-old pictureof the sky. In this respect, the scientific interest of such collection is potentially equivalent tothat of all the other world-wide astronomical plate archives. For this reason, the goals andobjectives of our WG and those of the PDPP task force attached to the IAU Commission 5 onAstronomical Data are shared; therefore, to the best interest of both groups, only one WG/TaskForce dealing with the preservation and digitization of this heritage from the past should bepreserved.Finally, a sensible issue not yet clearly answered, which would be decisive for a realisticestimation of project resources and timelines, is the level of accuracies achievable from the fitsimages of AC/CdC plates scanned with commercial scanners. This issue is equally relevant toall astronomical plate collections.