======= spPlate ======= :Summary: Combined spectra for one plate. The spPlate files contain the combined spectra for all exposures of a given plate. There are typically four 900s exposures which may have been taken in a single night, or over multiple nights. This page is an updated summary of the `SDSS2 spPlate data model`_ . :Naming Convention: ``spPlate-PLATE4-MJD5.fits``, where ``PLATE4`` is the zero-padded, four-digit plate number and ``MJD5`` is the five-digit MJD. :Regex: ``spPlate-[0-9]{4}-[0-9]{5}\.fits`` .. _`SDSS2 spPlate data model`: http://spectro.astro.princeton.edu/#dm_spplate Contents ======== ====== ======== ======== ================================================= Number EXTNAME Type Contents ====== ======== ======== ================================================= HDU0_ FLUX IMAGE Flux in units of |flux|. HDU1_ IVAR IMAGE Inverse variance (\ :math:`1/\sigma^2`) for HDU 0 HDU2_ ANDMASK IMAGE AND mask HDU3_ ORMASK IMAGE OR mask HDU4_ WAVEDISP IMAGE Wavelength dispersion in pixels HDU5_ PLUGMAP BINTABLE Plug-map structure from plPlugMapM file HDU6_ SKY IMAGE Average sky flux in units of |flux|. ====== ======== ======== ================================================= .. |flux| replace:: 10\ :sup:`-17` erg/s/cm\ :sup:`2`\ /Å FITS Header Units ================= HDU0 ---- EXTNAME = FLUX Data: FITS image [float64] HDU1 ---- EXTNAME = IVAR Data: FITS image [float64] HDU2 ---- EXTNAME = ANDMASK Data: FITS image [int32] HDU3 ---- EXTNAME = ORMASK Data: FITS image [int32] HDU4 ---- EXTNAME = WAVEDISP Data: FITS image [float64] .. _spplate-hdu5-plugmap: HDU5 ---- EXTNAME = PLUGMAP Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ ======== ========= ==== ======================================== Header Value Type Comment ======== ========= ==== ======================================== XTENSION BINTABLE str Binary table written by MWRFITS v1.8 BITPIX 8 int Required value NAXIS 2 int Required value NAXIS1 250 int Number of bytes per row NAXIS2 NFIBER int Number of rows PCOUNT 0 int Normally 0 (no varying arrays) GCOUNT 1 int Required value TFIELDS 34 int Number of columns in table ======== ========= ==== ======================================== Required Data Table Columns ~~~~~~~~~~~~~~~~~~~~~~~~~~~ ================= ======== ======= Column Type Comment ================= ======== ======= OBJID int32[5] HOLETYPE char[6] RA double DEC double MAG float[5] STARL float EXPL float DEVAUCL float OBJTYPE char[16] XFOCAL double YFOCAL double SPECTROGRAPHID int32 FIBERID int32 THROUGHPUT int32 PRIMTARGET int32 SECTARGET int32 OFFSETID int32 SCI_EXPTIME float SOURCETYPE char[7] LAMBDA_EFF float ZOFFSET float BLUEFIBER int32 BOSS_TARGET1 int64 BOSS_TARGET2 int64 ANCILLARY_TARGET1 int64 ANCILLARY_TARGET2 int64 RUN int32 RERUN char[5] CAMCOL int32 FIELD int32 ID int32 CALIBFLUX float[5] CALIBFLUX_IVAR float[5] SFD_EBV float ================= ======== ======= HDU6 ---- EXTNAME = SKY FITS Image: Average sky flux Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ ======== ====== ==== ======================================== Header Value Type Comment ======== ====== ==== ======================================== XTENSION IMAGE str Image Extension created by MWRFITS v1.4a BITPIX -32 int Data is 32-bit float NAXIS 2 int Number of data axes NAXIS1 NPIX int Width NAXIS2 NFIBER int Height ======== ====== ==== ======================================== Data: FITS image [float64] Notes and Examples ================== Additional HDUs may be present for engineering purposes, but are not supported and are subject to change. Users should refrain from using HDUs not listed here. There are two masks, an "AND" mask and an "OR" mask. The spectra are constructed from 3 or more 15-minute observations, and the "AND" mask bits are set if that bit is set for each and every input observation. The "OR" mask bits are set if that bit is set for any of the observations. Usually, only "AND" mask is of interest. The mask bits are set as follows. The authoritative definition of mask bits is in `idlutils/data/sdss/sdssMaskbits.par`_, with an alternate parsing at the `data release documentation`_. They are included here for convenience: .. _`idlutils/data/sdss/sdssMaskbits.par`: http://www.sdss3.org/svn/repo/idlutils/trunk/data/sdss/sdssMaskbits.par .. _`data release documentation`: http://www.sdss3.org/dr10/algorithms/bitmasks.php === ============== ========================================================================================= Bit Name Description === ============== ========================================================================================= 0 NOPLUG Fiber not listed in plugmap file 1 BADTRACE Bad trace from routine TRACE320CRUDE 2 BADFLAT Low counts in fiberflat 3 BADARC Bad arc solution 4 MANYBADCOLUMNS >10% pixels are bad columns 5 MANYREJECTED >10% pixels are rejected in extraction 6 LARGESHIFT Large spatial shift between flat and object pos'n 7 BADSKYFIBER Sky Fiber shows extreme residuals 8 NEARWHOPPER Within 2 fibers of a whopping fiber (deprecated) 10 SMEARIMAGE Smear available for red and blue cameras (deprecated) 11 SMEARHIGHSN S/N sufficient for full smear fit (deprecated) 12 SMEARMEDSN S/N only sufficient for scaled median fit (deprecated) 16 NEARBADPIXEL Bad pixel within 3 pixels of trace 17 LOWFLAT Flat field less than 0.5 18 FULLREJECT Pixel fully rejected in extraction (INVVAR=0) 19 PARTIALREJECT Some pixels rejected in extraction 20 SCATTEREDLIGHT Scattered light significant 21 CROSSTALK Cross-talk significant 22 NOSKY Sky level unknown at this wavelength (INVVAR=0) 23 BRIGHTSKY Sky level > flux + 10*(flux error) AND sky > 2.0 * median(sky,99 pixels) 24 NODATA No data available in combine B-spline (deprecated; INVVAR=0) 25 COMBINEREJ Rejected in combine B-spline 26 BADFLUXFACTOR Low flux-calibration or flux-correction factor 27 BADSKYCHI Relative |chi2| > 3 in sky residuals at this wavelength 28 REDMONSTER Contiguous region of bad |chi2| in sky residuals (with threshhold of relative |chi2| > 3) === ============== ========================================================================================= .. |chi2| replace:: :math:`\chi^2` When low numbered bits (<16) are set, those will be set for half of the spectra: either the blue or red spectrograph. The higher-numbered bits (>=16) are set for individual pixels. Which mask bits are important? The conditions that are considered very bad are already used to set the errors to infinity for the effected pixels (specifically, the inverse variance is set to zero). The most useful mask bit to look at is BRIGHTSKY, which indicates when the sky is so bright relative to the object that perhaps one shouldn't trust any of the object flux there. Our reported errors are meant to include sky-subtraction errors, but there are instances (particularly around 5577) where these errors may be untrustworthy. Dispersion and sky: The dispersion per pixel and the sky flux are computed at each pixel by re-weighting the individual spectra at each pixel according to their formal errors. This re-weighting is only approximate. Sky wavelengths: Note that the sky lines are slightly shifted in the reductions because we transform the velocities to the barycenter of the solar system. Each exposure that contributes to the co-added spectra will have slightly different barycenter correction, so the "average sky" contains a superposition of these slightly-offset sky lines. These shifts keep the object spectra as-measured at the barycenter, regardless of the time of year or the Earth's rotation relative to the spectroscopic targets. Doodles ======= See sdR_ .. _sdR: ./sdR.rst Superscript\ :sup:`superscript` Subscript\ :sub:`subscript` Generate html with:: rst2html.py -gdts datamodel_test.rst datamodel_test.html With docutils installed by MacPorts_, I have to do:: rst2html-2.7.py -gdts datamodel_test.rst datamodel_test.html .. _MacPorts: http://www.macports.org