General description: idGang files come in two types, astrometric and photometric. There is one astrometric gang file for each field and astrometric row. There is one photometric gang file for each field and photometric column. The astrometric gangs files have 13 HDUs: a primary, 6 "postage stamp" HDUs for each CCD and 6 "bright star measured parameters" HDUs for each CCD. The photometric gangs files have 16 HDUs: a primary, 5 "quartile" HDUs for each CCD, 5 "postage stamp" HDUs for each CCD and 5 "bright star measured parameters" HDUs for each CCD.
Naming convention:
Astrometric: idGang-[RUN]-r[6-9]-[FRAME].fit (RUN is 6 digits, FRAME is 4 digits)
Photometric: idGang-[RUN]-c[1-6]-[FRAME].fit (RUN is 6 digits, FRAME is 4 digits)
Approximate size:
Astrometric: 1131840 bytes.
Photometric: 397440 bytes.
File type: FITS
Read by products: photoop (others?)
Written by products: DA
There is one HDU of this format for each CCD handled by the DA CPU. Note that every HDU of this format contains an exact number of rows in its binary table (100 for astrometric HDUs), but not every row contains real data around a star. The header keyword BSCOUNT specifies the actual number of stars detected; the rows after the first BSCOUNT rows should be ignored. This is done for speed purposes in the DA system. Thus, NAXIS2 is always equal to 100 for astrometric HDUs. In the header keyword EXTNAME, a two digit identifier is given for the location of the CCD in the imaging camera.
These HDUs are not in standard FITS format, which does not allow the USHORT data type.
An example header is given below:
XTENSION= 'BINTABLE' BITPIX = 8 NAXIS = 2 NAXIS1 = 1686 NAXIS2 = 100 PCOUNT = 0 GCOUNT = 1 TFIELDS = 3 EXTNAME = 'STAMP 74' CAMCOL = 4 / Column in imaging camera PSSIZE = 29 / Postage Stamp Size BSCOUNT = 10 / Number of Bright Stars PIX4STAR= 5 / Number of pixels in 3x3 needed for star STAR5X5 = 1 / True means use 5x5 for star finding STARDIST= 20 / Minimum distance between adjacent stars SDISTRIB= 1 / True means distribute stamps over frame STHRESHL= 894 / Star threshold - lo column numbers STHRESHR= 894 / Star threshold - hi column numbers SABSKYL = 15 / Value to add to sky level = threshold - lo colu SABSKYR = 15 / Value to add to sky level = threshold - hi colu SSATL = 65035 / Star saturation - lo column numbers SSATR = 65035 / Star saturation - hi column numbers SLOCOLL = 15 / Number of lo cols to skip for lo column numbers SLOCOLR = 0 / Number of lo cols to skip for hi column numbers SHICOLL = 0 / Number of hi cols to skip for lo column numbers SHICOLR = 15 / Number of hi cols to skip for hi column numbers TSHIFT = 64 / Bias scaling factor FRBIASL = 56414 / Left Frame bias x TSHIFT FRBIASR = 56201 / Right Frame bias x TSHIFT FRSKYL = 56289 / Left Mean Sky Value x TSHIFT FRSKYR = 56288 / Right Mean Sky Value x TSHIFT FROSCNL = 56192 / Left Mean Oscn Value x TSHIFT FROSCNR = 56194 / Right Mean Oscn Value x TSHIFT SKIPPED = 0 / Number of rows ignored TIMEROW = 0 / 10*Average time per row (usec) TIMEFRAM= 0 / 10*T to analyze PREVframe (usec),scaled to 1 li ASTODDOF= 1 / Astrometric odd column adjustment offset AUTHOR = 'Node=sdssad2 Type=astro Cr=3 Bd=1 #=6 Src=camera' TFORM1 = '841U ' / PostStamp ushorts TTYPE1 = 'PIXELMAP' / Postage Stamp subimage TUNIT1 = 'ADUs ' TFORM2 = '1I ' TTYPE2 = 'MIDROW ' / Frame row (data section) of middle pixel TFORM3 = '1I ' TTYPE3 = 'MIDCOL ' / Frame column (data section) of middle pixel END
There is one HDU of this format for each CCD handled by the DA CPU. Note that every HDU of this format contains an exact number of rows in its binary table (100 for astrometric HDUs), but not every row contains real data around a star. The header keyword BSCOUNT specifies the actual number of stars detected; the rows after the first BSCOUNT rows should be ignored. This is done for speed purposes in the DA system. Thus, NAXIS2 is always equal to 100 for astrometric HDUs. In the header keyword EXTNAME, a two digit identifier is given for the location of the CCD in the imaging camera.
Data from the focus chips are stored in the same fields as for the imaging chips, but with different meanings, as follows:
An example header is given below:
XTENSION= 'BINTABLE' BITPIX = 8 NAXIS = 2 NAXIS1 = 48 NAXIS2 = 100 PCOUNT = 0 GCOUNT = 1 TFIELDS = 12 EXTNAME = 'STAR 76 ' CAMCOL = 6 / Column in imaging camera BSCOUNT = 15 / Number of Bright Stars FOCFLAG = 0 / Focus code run flag SIGFILT = 1.200000 / Sigma used for gunn filter VARFILTL= 0.000000 / Variance (left) used for gunn filter VARFILTR= 0.000000 / Variance (right) used for gunn filter GAINFILL= 1.000000 / Amp Gain (left) used for gunn filter GAINFILR= 1.000000 / Amp Gain (right) used for gunn filter NMEDIAN = 1 / Number used in stokes medians RMEDIAN = -9999.000000 / Median of rmajor for Stars QMEDIAN = -9999.000000 / Median of Q for Stars UMEDIAN = -9999.000000 / Median of U for Stars AUTHOR = 'Node=sdssad2 Type=astro Cr=3 Bd=1 #=6 Src=camera' TFORM1 = '1J ' TTYPE1 = 'MIDROW ' / Frame row of the stamp's middle pixel. TFORM2 = '1J ' TTYPE2 = 'MIDCOL ' / Frame column of the stamp's middle pixel. TFORM3 = '1E ' TTYPE3 = 'ROWCENTROID' / Row position of star center. TUNIT3 = 'pixels ' TFORM4 = '1E ' TTYPE4 = 'ROWCENTROIDERR' / Row position of star center. (error) TUNIT4 = 'pixels ' TFORM5 = '1E ' TTYPE5 = 'COLCENTROID' / Column position of star center. TUNIT5 = 'pixels ' TFORM6 = '1E ' TTYPE6 = 'COLCENTROIDERR' / Column position of star center. (error) TUNIT6 = 'pixels ' TFORM7 = '1E ' TTYPE7 = 'RMAJOR ' / Major axis radius. TUNIT7 = 'pixels ' TFORM8 = '1E ' TTYPE8 = 'RMINOR ' / Minor axis radius. TUNIT8 = 'pixels ' TFORM9 = '1E ' TTYPE9 = 'ANGMAJORAXIS' / Major axis position angle. TUNIT9 = 'degrees ' TFORM10 = '1E ' TTYPE10 = 'PEAK ' / Peak of the gaussian fit. TUNIT10 = 'DNs ' TFORM11 = '1E ' TTYPE11 = 'COUNTS ' / Sum of counts over sky. TUNIT11 = 'DNs ' TFORM12 = '1J ' TTYPE12 = 'STATUSFIT' / 0=ok, less than 0 implies error. END
HDU's of this format are found in photometric gang files only. There are 5 of these HDUs, one per CCD in the column. Below, NAXIS2 will be equal to 2128. The TSHIFT keyword gives the amount by which each quartile value has been multiplied; e.g., if TSHIFT = 100, then each quartile value in the HDU is 100 times larger than the true value. This scaling allows us to calculate precise quartile values while maintaining pure integers. In EXTNAME, a two digit identifier is given for the location of the CCD in the imaging camera.
An example header is given below:
XTENSION= 'BINTABLE' BITPIX = 8 NAXIS = 2 NAXIS1 = 12 NAXIS2 = 2128 PCOUNT = 0 GCOUNT = 1 TFIELDS = 3 EXTNAME = 'QUART 12' CAMROW = 1 / Row in imaging camera TSHIFT = 64 / Quartile scaling factor HISTBINS= 260 / Num bins in quartile hists DBASE = 130 / Maximum delta for hist bases NQCALCL = 1064 / Number of quartiles calculated - lo col numbers NQCALCR = 1064 / Number of quartiles calculated - hi col numbers FRBIASL = 66690 / Left Frame bias x TSHIFT FRBIASR = 66142 / Right Frame bias x TSHIFT FRSKYL = 66540 / Left Mean Sky Value x TSHIFT FRSKYR = 66261 / Right Mean Sky Value x TSHIFT FROSCNL = 66498 / Left Mean Oscn Value x TSHIFT FROSCNR = 66222 / Right Mean Oscn Value x TSHIFT SKIPPED = 0 / Number of rows ignored QTNCUT = 570 / SigCut = qtNcut * 0.00527 * sigma AUTHOR = 'Node=sdssid2 Type=photo Cr=1 Bd=1 #=5 Src=camera' TFORM1 = '1J ' TTYPE1 = 'Q1 ' / 25th percentile TUNIT1 = 'ADUs x TSHIFT' TFORM2 = '1J ' TTYPE2 = 'Q2 ' / 50th percentile TUNIT2 = 'ADUs x TSHIFT' TFORM3 = '1J ' TTYPE3 = 'Q3 ' / 75th percentile TUNIT3 = 'ADUs x TSHIFT' END
There is one HDU of this format for each CCD handled by the DA CPU. Note that every HDU of this format contains an exact number of rows in its binary table (30 for photometric HDUs), but not every row contains real data around a star. The header keyword BSCOUNT specifies the actual number of stars detected; the rows after the first BSCOUNT rows should be ignored. This is done for speed purposes in the DA system. Thus, NAXIS2 is always equal to 30 for photometric HDUs. In the header keyword EXTNAME, a two digit identifier is given for the location of the CCD in the imaging camera.
These HDUs are not in standard FITS format, which does not allow the USHORT data type.
An example header is given below:
XTENSION= 'BINTABLE' BITPIX = 8 NAXIS = 2 NAXIS1 = 1686 NAXIS2 = 100 PCOUNT = 0 GCOUNT = 1 TFIELDS = 3 EXTNAME = 'STAMP 74' CAMCOL = 4 / Column in imaging camera PSSIZE = 29 / Postage Stamp Size BSCOUNT = 10 / Number of Bright Stars PIX4STAR= 5 / Number of pixels in 3x3 needed for star STAR5X5 = 1 / True means use 5x5 for star finding STARDIST= 20 / Minimum distance between adjacent stars SDISTRIB= 1 / True means distribute stamps over frame STHRESHL= 894 / Star threshold - lo column numbers STHRESHR= 894 / Star threshold - hi column numbers SABSKYL = 15 / Value to add to sky level = threshold - lo colu SABSKYR = 15 / Value to add to sky level = threshold - hi colu SSATL = 65035 / Star saturation - lo column numbers SSATR = 65035 / Star saturation - hi column numbers SLOCOLL = 15 / Number of lo cols to skip for lo column numbers SLOCOLR = 0 / Number of lo cols to skip for hi column numbers SHICOLL = 0 / Number of hi cols to skip for lo column numbers SHICOLR = 15 / Number of hi cols to skip for hi column numbers TSHIFT = 64 / Bias scaling factor FRBIASL = 56414 / Left Frame bias x TSHIFT FRBIASR = 56201 / Right Frame bias x TSHIFT FRSKYL = 56289 / Left Mean Sky Value x TSHIFT FRSKYR = 56288 / Right Mean Sky Value x TSHIFT FROSCNL = 56192 / Left Mean Oscn Value x TSHIFT FROSCNR = 56194 / Right Mean Oscn Value x TSHIFT SKIPPED = 0 / Number of rows ignored TIMEROW = 0 / 10*Average time per row (usec) TIMEFRAM= 0 / 10*T to analyze PREVframe (usec),scaled to 1 li ASTODDOF= 1 / Astrometric odd column adjustment offset AUTHOR = 'Node=sdssad2 Type=astro Cr=3 Bd=1 #=6 Src=camera' TFORM1 = '841U ' / PostStamp ushorts TTYPE1 = 'PIXELMAP' / Postage Stamp subimage TUNIT1 = 'ADUs ' TFORM2 = '1I ' TTYPE2 = 'MIDROW ' / Frame row (data section) of middle pixel TFORM3 = '1I ' TTYPE3 = 'MIDCOL ' / Frame column (data section) of middle pixel END
There is one HDU of this format for each CCD handled by the DA CPU. Note that every HDU of this format contains an exact number of rows in its binary table (30 for photometric HDUs), but not every row contains real data around a star. The header keyword BSCOUNT specifies the actual number of stars detected; the rows after the first BSCOUNT rows should be ignored. This is done for speed purposes in the DA system. Thus, NAXIS2 is always equal to 30 for photometric HDUs. In the header keyword EXTNAME, a two digit identifier is given for the location of the CCD in the imaging camera.
Data from the focus chips are stored in the same fields as for the imaging chips, but with different meanings, as follows:
An example header is given below:
XTENSION= 'BINTABLE' BITPIX = 8 NAXIS = 2 NAXIS1 = 48 NAXIS2 = 100 PCOUNT = 0 GCOUNT = 1 TFIELDS = 12 EXTNAME = 'STAR 76 ' CAMCOL = 6 / Column in imaging camera BSCOUNT = 15 / Number of Bright Stars FOCFLAG = 0 / Focus code run flag SIGFILT = 1.200000 / Sigma used for gunn filter VARFILTL= 0.000000 / Variance (left) used for gunn filter VARFILTR= 0.000000 / Variance (right) used for gunn filter GAINFILL= 1.000000 / Amp Gain (left) used for gunn filter GAINFILR= 1.000000 / Amp Gain (right) used for gunn filter NMEDIAN = 1 / Number used in stokes medians RMEDIAN = -9999.000000 / Median of rmajor for Stars QMEDIAN = -9999.000000 / Median of Q for Stars UMEDIAN = -9999.000000 / Median of U for Stars AUTHOR = 'Node=sdssad2 Type=astro Cr=3 Bd=1 #=6 Src=camera' TFORM1 = '1J ' TTYPE1 = 'MIDROW ' / Frame row of the stamp's middle pixel. TFORM2 = '1J ' TTYPE2 = 'MIDCOL ' / Frame column of the stamp's middle pixel. TFORM3 = '1E ' TTYPE3 = 'ROWCENTROID' / Row position of star center. TUNIT3 = 'pixels ' TFORM4 = '1E ' TTYPE4 = 'ROWCENTROIDERR' / Row position of star center. (error) TUNIT4 = 'pixels ' TFORM5 = '1E ' TTYPE5 = 'COLCENTROID' / Column position of star center. TUNIT5 = 'pixels ' TFORM6 = '1E ' TTYPE6 = 'COLCENTROIDERR' / Column position of star center. (error) TUNIT6 = 'pixels ' TFORM7 = '1E ' TTYPE7 = 'RMAJOR ' / Major axis radius. TUNIT7 = 'pixels ' TFORM8 = '1E ' TTYPE8 = 'RMINOR ' / Minor axis radius. TUNIT8 = 'pixels ' TFORM9 = '1E ' TTYPE9 = 'ANGMAJORAXIS' / Major axis position angle. TUNIT9 = 'degrees ' TFORM10 = '1E ' TTYPE10 = 'PEAK ' / Peak of the gaussian fit. TUNIT10 = 'DNs ' TFORM11 = '1E ' TTYPE11 = 'COUNTS ' / Sum of counts over sky. TUNIT11 = 'DNs ' TFORM12 = '1J ' TTYPE12 = 'STATUSFIT' / 0=ok, less than 0 implies error. END