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Quality Control and
Data Processing

CAL | HC | refs | QC
Trending & QC1
   ZIMPOL phot std
QC links:
SPHERE: ZIMPOL photometric standard star
photometric zeropoint in V, R and I
Strehl ratio of acquired source
QC1 database (advanced users): browse | plot

The SPHERE calibration plan includes the observations of

  • IRDIS CI/DBI: photometric standard stars and astrometric standard stars
  • IFS: photometric standard stars and astrometric standard stars
  • ZIMPOL-IMG: photometric standard stars and astrometric standard stars
  • ZIMPOL-POL: unpolarized and polarized polarimetric standard stars

ZIMPOL photometric standard stars are acquired once a month in imaging mode in three broad band filters, under photometric conditions, once with closed loop and once with open loop, but both setups without coronograph. A further setup parameters are the neutral density filter.

ZIMPOL photometric standard star observation raw frame.

ZIMPOL photometric standard star observation.

ZIMPOL Photometric zeropoint


FITS key QC1 database: table, name definition class* HC_plot** more docu
QC.ZPOINT sphere_zimpol_stdphot_img..qc_zpoint photometric zeropoint HC [docuSys coming]
QC.ZPOINTCORR sphere_zimpol_stdphot_img..qc_zpoint_corrND ZP corrected for ND filter HC [docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter
**There might be more than one.


Photometric standard standard stars are acquired regularly in three broad band filters V, N_R and N_I in open loop and closed loop. No airmass dependent extinction correction is applied. The neutral density filter correction is applied. The closed loop observations are monitored.

Scoring&thresholds ZIMPOL Photometric zeropoint

The values are not scored.


  • The pipeline recipe was introduced in 2019. Observations have been processed from 2015-04 on.
  • Observations acquired before 2017-01 are based on targets not supported by the standard star catalogue, hence no zeropoints are available in the period before 2017-01.

Algorithm ZIMPOL Photometric zeropoint

The sky is subtracted via a numerical aperture and the counts are integrated.

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