Common Vocabulary
LSST Data Management
This document defines common vocabulary that should be used when naming columns in database schema and variables in transient classes. It also defines units and types.
Names for columns/attributes defining errors were omitted. To build them, append "Err" after columns' name (eg raErr, declErr). All error columns use the same units as the columns, for which the error is defined.
used name  unit  type  full name  comments

ra  degrees  int64  right ascension 

decl  degrees  int64  declination  dec is a reserved word in most DBMSes

uErrA  arcsec  float  Large dimension of the position error ellipse, assuming gaussian scatter  for u filter

uErrB  arcsec  float  Small dimension of the position error ellipse, assuming gaussian scatter  for u filter

uErrTheta  degrees  float  Orientation of the position error ellipse  for u filter

radesys   string(5)  Type of WCS used  Obsolete in ICRS

equinox   float  Equinox of the WCS  Obsolete in ICRS

equinox   int32  equinox of World Coordinate System (different type than previous) 

ctype1   string(20)  Coordinate projection type, axis 1 

ctype2   string(20)  Coordinate projection type, axis 2 

crpix1   float  Coordinate reference pixel, axis 1 

crpix2   float  Coordinate reference pixel, axis 2 

crval1   double  Coordinate value 1 @reference pixel 

crval2   double  Coordinate value 2 @reference pixel 

cunit1   varchar(10)  X axis units 

cunit2   varchar(10)  Y axis units 

cdelt1   float   Obsolete by cd_xx terms?

cdelt2   float   Obsolete by cd_xx terms?

cd11   float  First derivative of coordinate 1 w.r.t. axis 1 

cd21   float  First derivative of coordinate 2 w.r.t. axis 1 

cd12   float  First derivative of coordinate 1 w.r.t. axis 2 

cd22   float  First derivative of coordinate 2 w.r.t. axis 2 

ra_ll  degrees  double  ra for the lowleft corner  probably something more fancy needed

decl_ll  degrees  double  decl for the lowleft corner  probably something more fancy needed

ra_lr  degrees  double  ra for the lowright corner  probably something more fancy needed

decl_lr  degrees  double  decl for the lowright corner  probably something more fancy needed

ra_ul  degrees  double  ra for the upperleft corner  probably something more fancy needed

decl_ul  degrees  double  decl for the upperleft corner  probably something more fancy needed

ra_ur  degrees  double  ra for the upperright corner  probably something more fancy needed

decl_ur  degrees  double  decl for the upperright corner  probably something more fancy needed

dateObs   datetime  Date/Time? of observation start (UTC) 

taiObs   datetime  time of shutter open  international atomic time

mjdObs   double  MJD of observation start 

expTime   float  Duration of exposure 

darkTime   float  Total elapsed time from exposure start to end of read 

taiDark   double  time of shutter closed  during the exposure, if there was such an occasion; see Kem Cook for details. International atomic time. There also could be a situation when the shutter was closed and reopened multiple times during the exposure. In this case, a more complicated data structure is needed?

tDark   float  Dark time length during exposure (clouds, etc).  Since this can happen multiple times (see comment for MJDdark attribute), a more complex data structure may be needed

texp   float  Exposure time  for this particular element, eg Amplifier, CCD

zd   float  Zenith distance at observation midpoint 

airmass   float  Airmass value for the Amp reference pixel  preferably center, but not guaranteed

temperature  celsius  float  

wavelength   float  wavelength 

telAngle  degrees  float  Orientation angle of the telescope w.r.t sky  This is different from camera orientation w.r.t sky (encapsulated in WCS), since telescope is on altaz mount

azimuth  degrees  float  Azimuth of observation  preferably at center of exposure at center of image and including refraction correction, but none of this is guaranteed

alt  degrees  float  Altitude of observation  preferably at center of observation at center of image and including refraction correction, but none of this is guaranteed

elevation  degrees  float  same as alt? 

zpt   double  Photometric zero point magnitude 

psf_nstar   int32  Number of stars used for PSF measurement 

psf_apcorr   float  Photometric error due to imperfect PSF model (aperture correction) 

psf_sigma1   float  Inner Gaussian sigma for the composite fit (XXX) 

psf_sigma2   float  Outer Gaussian sigma for the composite fit (XXX) 

psf_b   float  Ratio of inner PSF to outer PSF (XXX) 

psf_b_2G   float  Ratio of Gaussian 2 to Gaussian 1 at origin (XXX) 

psf_p0   float  The value of the power law at the origin (XXX) 

psf_beta   float  The slope of the power law (XXX) 

psf_sigmap   float  Width parameter for the power law (XXX) 

psf_nprof   float  Number of profile bins (XXX) 

fwhm   float  Effective PSF width 

sigma_x   float  

sigma_y   float  

posAngle   float   psf related

peak   float   psf related

x0   float   psf related

x1   float   psf related

uMagnitude   double  magnitude (weighted average)  for u filter

uPetroMag   double  petrosian magnitude  for u filter

uApMag   double  aperture magnitude  for u filter

uIxx   float  Adaptive second moment  for u filter

uIyy   float  Adaptive second moment  for u filter

uIxy   float  Adaptive second moment  for u filter

uAmplitude   float  amplitude of magnitude variations  for u filter

uPeriod   float  period of magnitude variations  for u filter

primaryPeriod   float  Average period across all filters 

uTimescale  days  float  timescale of flux variations  for u filter

uNumObs    int32  number of measurements in the lightcurve  for u filter

uVarProb  %  int16  probability of variability. 100% = variable object  for u filter

bias   float  Bias level for the calibrated image 

gain   float  Gain value for the amplifier 

rdNoise  electrons  float  Read noise value  for this particular element, eg AmpExposure

sky   float  The average sky level in the frame 

skySig   float  Sigma of distribution of sky values 

u_fringeTime   datetime  Time when corresponding CMFringeExposure was processed  for u filter

u_flatTime   datetime  Time when corresponding CMFlatExposure was processed  for u filter

Image pixel array properties    

binX   int16  binning in Xcoordinate 

binY   int16  binning in Ycoordinate 

sizeX   int16  Size of the image in Xdirection (along rows; binned pixels)  Ignores overscan but includes regions that may be considered outside of the data portion of the image

sizeY   int16  Size of the image in Ydirection (along columns; binned pixels)  Ignores overscan but includes regions that may be considered outside of the data portion of the image

averPixelValue   float  average pixel value 

stdevPixelValue   float  standard deviation of average pixel value 

url    string  logical url of the corresponding FITS file 

nCombine    int32  Number of images coadded to create a deeper image 

probability  %  int8  Probability that given object is of given type 

sizeRa   float  size of ra  this appears in postage stamp table

sizeDecl   float  size of decl  this appears in postage stamp table

mops related    

a   float  semimajor axis of the orbit (AU) 

incl  degrees  float  inclination of the orbit 

e   float  eccentricity of the orbit 

periTAI   float  TAI of the perihelion passage (comets) 

periDist   float  Perihelion distance (AU) 

omega   float  argument of perihelion 

node   float  longitude of the ascending node 

meanAnom   float  mean anomaly of the orbit 

qual   float  measure of the accuracy of the derived orbit, classification, etc.  can be more than one. Placeholder

various ids    

alertId    int32  Id of an Alert 

amplifierId    int16  Id of an Amplifier 

ccExposureId    int64  Id of CCD Exposure 

filterId    int8  Id of a Filter 

objectId    int64  Id of an Astronomical Object 

movingObjectId    int64  Id of a Moving Object 

visitId    int32  Id of a Visit 

flatExposureId    int32  Id of a Flat Exposure 

biasExposureId    int32  Id of a Bias Exposure 

darkExposureId    int32  Id of a Dark Exposure 

cmFlatExposureId    int32  Id of a Calibrated Master Flat Exposure 

subtractedExposureId    int32  Id of a Subtracted Exposure 

varianceExposureId    int32  Id of a Variance Exposure
