Hi,
The image header is bellow:
SIMPLE = T / Fits standard
BITPIX = -32 / Bits per pixel
NAXIS = 2 / Number of axes
NAXIS1 = 2048 / Axis length
NAXIS2 = 1489 / Axis length
EXTEND = F / File may contain extensions
ORIGIN = 'NOAO-IRAF FITS Image Kernel July 2003' / FITS file originator
DATE = '2007-09-28T12:36:30' / Date FITS file was generated
IRAF-TLM= '20:36:52 (28/09/2007)' / Time of last modification
OBJECT = '11 S ' / Name of the object observed
TAI = 4464229733.94 / 1st row - Number of seconds since Nov 17 1858
RA = 193.86719 / 1st row - Right ascension of telescope boresigh
DEC = 2.470158 / 1st row - Declination of telescope boresight (d
SPA = 90.385 / 1st row - Camera col position angle wrt north (
IPA = 43.476 / 1st row - Instrument rotator position angle (de
IPARATE = 0.0002 / 1st row - Instrument rotator angular velocity (
AZ = 299.73242 / 1st row - Azimuth (encoder) of tele (0=N?) (de
ALT = 41.118844 / 1st row - Altitude (encoder) of tele (de
FOCUS = -999999999999.999999 / 1st row - Focus piston (microns?)
DATE-OBS= '2000-05-05' / 1st row - TAI date
TAIHMS = '07:48:53.93' / 1st row - TAI time (HH:MM:SS.SS) (TAI-UT = appr
COMMENT TAI,RA,DEC,SPA,IPA,IPARATE,AZ,ALT,FOCUS at reading of col 0, row 0
BUNITS = 'ADUs '
TELESCOP= '2.5m '
TIMESYS = 'TAI '
RUN = 1462 / Run number
FRAME = 461 / Frame sequence number within the run
CCDLOC = 14 / Survey location of CCD (e.g., rowCol)
STRIPE = 11 / Stripe index number (23 <--> eta=0)
STRIP = 'S ' / Strip in the stripe being tracked.
FLAVOR = 'science ' / Flavor of this run
SYS_SCN = 'mean ' / System of the scan great circle (e.g., mean)
EQNX_SCN= 2000.00 / Equinox of the scan great circle. (years)
NODE = 95.00000 / RA of the great circle's ascending node (deg)
INCL = 2.50000 / Great circle's inclination wrt cel. eq. (deg)
XBORE = 22.74 / Boresight x offset from the array center (mm)
YBORE = 0.00 / Boresight x offset from the array center (mm)
EXPTIME = '53.907456' / Exposure time (seconds)
SYSTEM = 'FK5 ' / System of the TCC coordinates (e.g., mean)
CCDMODE = 'DRIFT ' / 'STARING' or 'DRIFT'
C_OBS = 26322 / CCD row clock rate (usec/row)
COLBIN = 1 / Binning factor perpendicular to the columns
ROWBIN = 1 / Binning factor perpendicular to the rows
DAVERS = 'v14_24 ' / Version of DA software
COMMENT CCD-specific parameters
CAMROW = 1 / Row in the imaging camera
BADLINES= 0 / Number of bad lines in frame
EQUINOX = 2.00000000000000E+03
SOFTBIAS= 1000 / software "bias" added to all DN
FLUX20 = 1.88043000000000E+03 / Number of DN in 20th mag object
FLUX0 = -9.9990000000000E+03 / Number of DN in 0th mag object
FCALI_ID= 'None '
SKY = 1.59980000000000E+02 / Approx. sky level (DN)
BUNIT = 'DNs '
FILTER = 'r ' / filter used
CAMCOL = 4 / column in the imaging camera
VERSION = 'v5_4_24 '
DERV_VER= 'v8_16 '
ASTR_VER= 'v5_16 '
ASTRO_ID= '2003-07-09T16:53:02 06073'
BIAS_ID = 'PS '
FRAME_ID= '2003-07-14T23:42:00 28595'
KO_VER = 'devel '
PS_ID = '2003-07-09T11:23:48 21176 camCol 4'
ATVSN = 'v5_16 ' / ASTROTOOLS version tag
RADECSYS= 'ICRS ' / International Celestial Ref. System
CTYPE1 = 'RA---TAN'
CTYPE2 = 'DEC--TAN'
CUNIT1 = 'deg '
CUNIT2 = 'deg '
CRPIX1 = 1.02450000000000E+03 / Column Pixel Coordinate of Ref. Pixel
CRPIX2 = 7.44500000000000E+02 / Row Pixel Coordinate of Ref. Pixel
CRVAL1 = 1.94435716340000E+02 / RA at Reference Pixel
CRVAL2 = 2.57240785000000E+00 / DEC at Reference Pixel
CD1_1 = 8.30431860597186E-07 / RA degrees per column pixel
CD1_2 = 1.10001297896051E-04 / RA degrees per row pixel
CD2_1 = 1.09997822265625E-04 / DEC degrees per column pixel
CD2_2 = -7.8793010752684E-07 / DEC degrees per row pixel
Thank you very much!I use the WCSCTRAN task,and the result is same with rd2xy.I can't understand why it is a negtive number,and where's the object's position in the image.Because i want to trim the image with the object in the center.Best
yanqin