General description: idR files are the raw data output by the SDSS imaging camera. HDU0 is a 2128x1361 array of INTs, in unsigned format (this is a violation of the FITS convention). Overscan and bias location is stored in header. Files are typically stored in unix compressed form, with extension '.Z'.
Naming convention: idR-[RRRRRR]-[b][c]-[FFFF].fit.Z, where "RRRRRR" is the 6-digit run number, "b" is the band (u, g, r, i, or z), "c" is the camcol, and "FFFF" is the 4-digit field number. Field numbers are defined such that the same field number in different bands subtend the same solid angle on the sky.
idRR-[RRRRRR]-[b][c]-[FFFF].fit.Z, where "RRRRRR" is the 6-digit run number, "b" is the band (u, g, r, i, or z), "c" is the camcol, and "FFFF" is the 4-digit frame number. Frame numbers are defined such that the same frame number in different bands were taken in the same interval of time. idR files are hard-linked to idRR files at APO, so they represent the exact same data but with different names.
The azimuth ("AZ") given in the headers is not standard azimuth. It is in degrees East of South (or 180 minues the standard azimuth). Note that the comment in the headers of the idRs ("(0=N?)") is therefore incorrect.
Approximate size: 2 Mbytes (compressed).
File type: FITS
Read by products: photoop (others?)
Written by products: ???
Example header:
SIMPLE = F / FIT STANDARD BITPIX = 16 / FITS BITS/PIXEL NAXIS = 2 / NUMBER OF AXES NAXIS1 = 2128 / WIDTH (TOTAL!) NAXIS2 = 1361 / HEIGHT (TOTAL!) SDSS / THIS HEADER CONTAINS SPECIAL SDSS KEYWORDS UNSIGNED / UNSIGNED DATA - NO BSCALE OR BZERO KEYWORDS TAI = 4709572215.57 / 1st row Number of seconds since Nov 17 1858 RA = 121.00000 / 1st row RA of telescope boresight (deg) DEC = 30.000000 / 1st row Dec of telescope boresight (degrees) SPA = 0.000 / 1st row Cam col position angle wrt N (deg) IPA = 0.000 / 1st row Inst rotator position angle (deg) IPARATE = NaN / 1st row Inst rotator anglr velocity (deg/sec) AZ = 0.000000 / 1st row Azimuth (encoder) of tele (0=N?) (deg) ALT = 0.000000 / 1st row Altitude (encoder) of tele (degrees) FOCUS = 50.000000 / 1st row - Focus piston (microns?) DATE-OBS= '2008-02-12' / 1st row - TAI date TAIHMS = '22:30:15.56' / 1st row TAI time HH:MM:SS.SS DATASUM = '487972055' / Data checksum created 2008-02-12T22:30:51 CHECKSUM= 'UaAGaV3FUZ9FaZ9F' / HDU checksum created 2008-02-12T22:30:51 COMMENT TAI,RA,DEC,SPA,IPA,IPARATE,AZ,ALT,FOCUS at reading of col 0, row 0 BUNITS = 'ADUs ' ORIGIN = 'SDSS ' TELESCOP= '2.5m ' TIMESYS = 'TAI ' RUN = 7322 / Run number FRAME = 10 / Frame sequence number within the run CCDLOC = 31 / Survey location of CCD (e.g., rowCol) STRIPE = 100 / Stripe index number (23 <--> eta=0) STRIP = 'O ' / Strip in the stripe being tracked. FLAVOR = 'bias ' / Flavor of this run OBSERVER= 'swatters' / Observer SYS_SCN = 'mean ' / System of the scan great circle (e.g., mean) EQNX_SCN= 2000.00 / Equinox of the scan great circle. (years) NODE = 92.68115 / RA of the great circle's ascending node (deg) INCL = 0.04635 / Great circle's inclination wrt cel. eq. (deg) XBORE = 0.00 / Boresight x offset from the array center (mm) YBORE = 0.00 / Boresight x offset from the array center (mm) OBJECT = '100 O ' / e.g., 'stripe 50.6 degrees, north strip' EXPTIME = '53.907456' / Exposure time (seconds) EQUINOX = 'NaN ' / Equinox of the TCC coordinates (years) SYSTEM = 'Mount ' / 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 NLINES = 2048 / Number of lines in a frame DAVERS = 'v15_13_1' / Version of DA software SCDMETHD= 'linearDynamic' / scdMethod SCDWIDTH= 1280 / scdDisplayWidth SCDDECMF= 9 / scdDecimateFactor SCDOFSET= 0 / scdDisplayOffset SCDDYNTH= -20 / scdDynamicThresh SCDSTTHL= 30 / scdStaticThreshL SCDSTTHR= 30 / scdStaticThreshR SCDREDSZ= 41 / scdReduceSize SCDSKYL = 1799 / scdSkyLeft SCDSKYR = 1799 / scdSkyRight COMMENT CCD-specific parameters CAMCOL = 1 / Column in the imaging camera CAMROW = 3 / Row in the imaging camera FILTER = 'u ' / Filter (riugz olts) AMPL = 0 / which amp 0,1,2,3 corresponds to low pix AMPR = 1 / which amp 0,1,2,3 corresponds to high pix BADLINES= 0 / Number of bad lines in frame CCDSECL = '[21:1064,1:1361]' / Physical ccd section for low pixels OVERSECL= '[1:20,1:1361]' / Image section for overscan for low pix BIASSECL= '[21:40,1:1361]' / Image section for prescan for low pix DATASECL= '[41:1064,1:1361]' / Image section for data for low pixels CCDSECR = '[1065:2108,1:1361]' / Physical ccd section for high pixels DATASECR= '[1065:2088,1:1361]' / Image section for data for high pixels BIASSECL= '[2089:2108,1:1361]' / Image section for prescan for high pixels OVERSECR= '[2109:2128,1:1361]' / Image section for overscan for high pixels