CDROM/AJ/V114/P0850 Errors in the FK5 Catalog (Stone 1997) ================================================================================ Systematic Errors in the FK5 Catalog as Determined From CCD Observations in the Extragalactic Reference Frame Ronald C. Stone <1997, AJ, 114, 850> =1997AJ....114..850S ================================================================================ Abstract: This paper presents new positions for 689 FK5 stars determined directly in the extragalactic reference system from CCD scan observations made with the Flagstaff Astrometric Scanning Transit Telescope (FASTT). All the observations were made in 1994-1996 with an accuracy of ~ +/- 40 mas in each coordinate. When these positions are compared with their counterparts in the FK5 catalog, systematic errors in the FK5 are found that vary in both right ascension and declination and can be as large as 100 mas in magnitude. No magnitude-dependent errors in the FK5 were found. Moreover, the true error in FK5 star positions is determined to be ~ +/- 80 mas in both coordinates or two times the expected catalog positional errors. There is excellent agreement between the systematic errors in the FK5 found in this paper and those presented in Lindegren et al. (1995, A&A, 304, 44) comparing FK5 and Hipparcos 30-month star positions. By comparing corresponding FASTT and FK5 star positions, the link between the optical and extragalactic reference frames was determined and is given by the following rotations (Omega_x,Omega_y,Omega_z) = (3+/-5, 25+/-5, 16+/-4) (s.e.) mas, which agree well with previous determinations made by other investigators. Two of the rotations (Omega_y,Omega_z) are significantly larger than their standard errors and, therefore, presumably real. Finally, since these rotations are small (<= 25 mas), the FK5 and extragalactic reference frames must be closely aligned to one another. File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table.dat 102 689 FK5 Star Positions Determined in the Extragalactic Reference Frame With the FASTT CCD Meridian Telescope -------------------------------------------------------------------------------- Byte-by-byte Description of file: table.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 3 I3 --- Num Running number 4- 9 I6 --- FK5 FK5 star number 10-17 I8 --- HD HD designation 18-22 F5.1 mag V V magnitude taken from FK5 catalog 23-26 I4 h RAh Right ascension, J2000 27-29 I3 min RAm R.A. 30-37 F8.4 s RAs R.A. 38-42 F5.1 .0001s e_RA Standard error in RA 43-46 I4 --- o_RA Number of times observed in RA 47-54 F8.3 yr epRA Mean epoch of RA coordinate (+ 1900) 55-62 F8.3 s/100yr pmRA Proper motion in RA taken from FK5 63-64 2X --- --- Blank 65 A1 --- DE- Declination sign, J2000 66-67 I2 deg DEd Declination, J2000 68-70 I3 arcmin DEm Dec. 71-77 F7.3 arcsec DEs Dec. 78-81 I4 .001arcsec e_DE Standard error in the Dec. 82-85 I4 --- o_DE Number of times observed in Dec. 86-93 F8.3 yr epRA Mean epoch of Dec. coordinate (+ 1900) 94-112 F9.2 arcsec/100yr pmRA Proper motion in Dec. taken from FK5 -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 27-Sep-1997