Quality Control and
Data Processing

HC PLOTS
zeropoint u_SDSS
zeropoint g_SDSS
zeropoint r_SDSS
zeropoint i_SDSS
zeropoint z_SDSS
zeropoint B_JOHN
zeropoint V_JOHN
fwhm u_SDSS
fwhm g_SDSS
fwhm r_SDSS
fwhm i_SDSS
fwhm z_SDSS
fwhm B_JOHN
fwhm V_JOHN
ellipticity u_SDSS
ellipticity g_SDSS
ellipticity r_SDSS
ellipticity i_SDSS
ellipticity z_SDSS
ellipticity B_JOHN
ellipticity V_JOHN
QC1 database (advanced users): browse | plot

During normal VST/OmegaCAM operations standard star frames (DPR.TYPE = STD,ZEROPOINT) are taken on the same night matching each filter for which science data was obtained. The data consists of a single standard star field of similar airmass and identical filter. To monitor the ambient conditions (extinction) another standard star observation is made of the polar field (DPR.TYPE = STD,EXTINCTION) at the beginning, middle, and end of the night.

The standard frame is bias corrected, flat-fielded, background subtracted, and trimmed. SExtractor is run on the image and is cross-matched to sources present in the external standard star catalogue (REFERENCE_STAR_CATALOG). The apparent magnitudes of the SExtractor catalogue and the absolute magnitudes of the REFERENCE_STAR_CATALOG is used to define the zeropoints for each detector. The zeropoints monitored for the health check plots are derived from flux units of electrons/second.

The pipeline creates four output frames from its standard star recipe (omega_standard_star): a reduced standard star image (OC_PSTD_<DATE>_1_1_normal_normal_<FILTER>.fits), a photometric fits table listing each secondary standard star source detected in each detector (OC_PPHO_<DATE>_1_1_normal_normal_<FILTER>.fits), a fits table listing the computed zeropoints for each detector (OC_PZPT_<DATE>_1_1_normal_normal_<FILTER>.fits), and a mask of bad pixels, saturated pixels, and satellite trails for the reduced standard star image (OC_PSMA_<DATE>_1_1_normal_normal_<FILTER>.fits).

The full OmegaCAM reduced standard frame (r_SDSS filter).

A single detector (ESO_CCD_#71) OmegaCAM reduced standard frame (r_SDSS filter).

A single detector (ESO_CCD_#71) OmegaCAM reduced standard mask (r_SDSS filter). A value of 1 indicates a bad pixel; otherwise 0.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.ZEROPOINT_ELECTRON	omegacam_std..qc_zeropoint_electron	detector zeropoint computed from flux units of e-/sec.	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

Following parameters are monitored for each of the filters: u_SDSS, g_SDSS, r_SDSS, i_SDSS, z_SDSS, B_JOHN, and V_JOHN:

• zeropoint as averaged over all 32 detectors
• zeropoint rms averaged over all 32 detectors
• zeropoints for each individual detector
• score outliers

Scoring&thresholds Standard Star Zeropoint

Very loose scoring applied.

History

Date	event
2012-12-05	System throughput increased by 5% due to washing of M1
2013-12-05	System throughput drop by about 0.6% within a few days early December, due to dust. Stable since then.
2014-03-27	The M1 was washed. This resulted in an improvement of ~3.8% in the mirror's reflectivity.
2020-11-15	CCD77 does not work; only displays random signal consistent with noise, PPRS-079377
2022-05-09	CCD77 started recording some coherent signal again

Algorithm Standard Star Zeropoint

The detector-specific zeropoint computed from flux units of electrons/second.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
[calculated by QC procedure]	omegacam_std..qc_delta_fwhm	difference (qc_std_seeing - qc_ambi_seeing) (arcsec) (QCscript)	HC		[docuSys coming]
QC.STD.SEEING	omegacam_std..qc_std_seeing	median Sextractor FWHM of detected sources with STAR_CLASS>=0.9 (arcsec)	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

Following parameters are monitored for each of the filters: u_SDSS, g_SDSS, r_SDSS, i_SDSS, z_SDSS, B_JOHN, and V_JOHN:

• image quality plotting the stellar source FWHM vs. the corrected (for airmass and waveband) DIMM seeing (arcsec)
• the difference in the standard star FWHM vs. the corrected DIMM seeing (arcsec)
• score outliers

A one-to-one comparison of the image quality (the FWHM of the stars matched from the secondary standard catalogue) achieved by OmegaCAM and the seeing as measured by the DIMM (converted to the STD star OB's airmass and waveband) are plotted against one another (in arcsec). The values for each of the 32 detectors is shown.

Scoring&thresholds Standard Star Image Quality

Not scored.

History

No major events.

Algorithm Standard Star Image Quality

The FWHM (arcsec) is measured only for sources identified as stellar (CLASS_STAR >= 0.90 from the SExtractor detection) and are contained in the pipeline product frame PRO.CATG=ZEROPOINTS. The DIMM seeing has been adjusted to the wavelength and airmass of the standard star observation.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.STD.ELLIPTICITY	omegacam_std..qc_std_ellipticity	median Sextractor ellipticity of detected sources with STAR_CLASS>=0.9	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

Following parameters are monitored for each of the filters: u_SDSS, g_SDSS, r_SDSS, i_SDSS, z_SDSS, B_JOHN, and V_JOHN:

• the stellar source ellipticity (1 - b/a) averaged over all 32 detectors
• the stellar source ellipticity rms averaged over all 32 detectors
• the stellar source ellipticity for each individual detector
• score outliers

Scoring&thresholds Standard Star Ellipticity

Very loose scoring applied.

History

No major events.

Algorithm Standard Star Ellipticity

The ellipticity (1 - b/a) is measured only for source identified as stellar (CLASS_STAR >= 0.90 from the SExtractor detection) and is contained in the pipeline product frame PRO.CATG=ZEROPOINTS