Quality Control Tables
This page provides quality control tables in FITS format for download. The tables are organised by month and compressed using gzip. For an explanation of the columns please see the database schema.
Monthly QC tables are available here
Some examples of checks which can be performed using these tables:
- Non photometric observations. Check the magnitude zero points, if they are way below the median value it means that the observations were obtained in non-photometric conditions. Note however that the Z and Y band calibrations in regions of high extinction (e.g. E(B-V)>2 as in VVV) may show deviations from the usual values due to the calibration method, not necessarily non-photometric conditions.
- Trailed images. High values of average ellipticity (larger than 0.2) means that images are probably trailed or out of focus.
- Astrometry. The median astrometric rms is 0.10 arcsec, with 99% of the images having better than 0.2 arcsec. Larger values indicate some problem (like again trailed images, double images or out of focus). A low number of standards used (less than 10) per detector is also suspicious.
- Aborted OBs. We process all the data we receive, even if it does not contain the full set of pawprint images. Check that the number of jitters is equal to the number of pawprints which made the stack.
- Weather conditions, moon position and phase, sky brightness, magnitude limits are all included in the table.
A subset of relevant keywords useful for QC are given below:
- obsairm
- Requested maximum airmass. Can be compared with observations using amstart and amend.
- obsfwhm
- Requested maximum seeing. Can be compared with observations using seeing.
- obstrans
- Requested sky transparency. According to ESO these are defined as
photometric (not visible clouds, transparency variations under 2%),
clear (less than 10% of sky above 30 deg elevation covered in clouds, transparency variations under 10%) and
thin cirrus (transparency variations above 10%) - obsmoondist
- Requested maximum separation from the moon.
- obsmoonfli
- Requested maximum moon phase.
- amstart, amend
- Airmass at start and end of observations.
- seeing
- Average seeing in detector (arcsec).
- njitter, nprov
- Number of jitter positions and actual number of frames combined for the stack.
If these two numbers are different then the OB is incomplete. - ellipticity
- Average ellipticity over the detector.
- magzpt, magzerr
- Zero point and rms.
- nightzpt, nightzrr
- Nightly zero point and rms.
- stdcrms, numbrms
- Astrometric fit accuracy and number of stars used.
- maglim
- Magnitude limit.
- skybright
- Sky brightness (mag/arcsec^2).
- obstatus, qcstatus
- ESO assigned status.