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VIRCAM Quality Control:
Photometric Standard Stars

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VIRCAM QC
Trending & QC1
   Phot.ZP
Pipeline
QC links:
photometric zeropoints | image_quality | ellipticity
 
QC PLOTS
  CURRENT HISTORY
photometric zeropoint
image quality
ellipticity
QC1 database (advanced users): browse | plot
   Click on CURRENT to see the current trending (Health Check).
   Click on HISTORY to see the historical evolution of the trending.


The 2MASS catalogue is used.

 

top photometric zeropoints

QC1 parameters

parameter QC1 database: table, name procedure

photometric zeropoint

vircam_photstd, qc_magzpt
- Photometric zeropoint for air mass (X) =1. The air mass is taken from the observation and the extinction coefficient is read from the static calibration PRO.CATG=PHOTCAL


The pipeline reads the extinction coefficients and the color terms from a static calibration with PRO.CATG=PHOTCAL_TABLE

From 2009-01-01 to 2010-10-01 the following table was used:

#
# file           phot.fits
# extensions     1
# --------------------------------------------
# XTENSION       1
# Number of columns 5
#
filter    |extinction|   offset|   columns|coleq
Z         |  0.000000| 0.000000|j_m,h_m   |3,-2
Y         |  0.010000| 0.000000|j_m,h_m   |2,-1
J         |  0.080000| 0.000000|j_m       |1
H         |  0.080000| 0.000000|h_m       |1
Ks        |  0.160000| 0.000000|k_m       |1
NB118     |  0.090000| 0.000000|j_m       |1

 

Since 2010-10-01 the following table is used:

#
# file           photcal_2010-01.fits
# extensions     1
# --------------------------------------------
# XTENSION       1
# Number of columns 5
#
filter    |extinction|   offset|   columns|coleq
Z         |  0.050000| 0.000000|j_m,h_m   |1.95,-0.95
Y         |  0.050000| 0.000000|j_m,h_m   |1.55,-0.55
J         |  0.050000| 0.000000|j_m,h_m   |0.93,0.07
H         |  0.050000| 0.000000|j_m,h_m   |0.06,0.94
Ks        |  0.050000| 0.000000|j_m,k_m   |0.02,0.98
NB118     |  0.050000| 0.000000|j_m,h_m   |1.10,-0.10

The following table will be used from 2011-06 -01 on:

#
# file           photcal_2010-12.fits
# extensions     1
# --------------------------------------------
# XTENSION       1
# Number of columns 5
#
filter    |extinction|   offset|   columns|coleq
Z         |  0.050000| 0.000000|j_m,h_m   |2.025,-1.025
Y         |  0.050000| 0.000000|j_m,h_m   |1.61,-0.61
J         |  0.050000| 0.000000|j_m,h_m   |0.923,0.077
H         |  0.050000| 0.000000|j_m,h_m   |0.032,0.968
Ks        |  0.050000| 0.000000|j_m,k_m   |0.01,0.99
NB118     |  0.050000| 0.000000|j_m,h_m   |1.10,-0.10
NB980     |  0.050000| 0.000000|j_m,h_m   |1.68,-0.68
      

VISTA M1 recoating interventions:

  • between 2009-08-19 and 2009-09-18
  • between 2011-03-04 and 2011-04-05
top image quality

 

QC1 parameters

parameter QC1 database: table, name procedure
qc_image_size vircam_photstd, qc_image_size - QC.IMAGE_SIZE is the median of the FWHM of all sources
qc_ellipticity vircam_photstd, qc_ellipticity - QC.ELLIPTICITY is the median of all (1-b/a) value. a being the semi major axis, b being the semi minor axis.

To compare the measured image quality with the seeing provided by the DIMM monitor, the transformation equations from Tokovinin, A., PASP 114, 1156 (2002) and from Martinez, P., Kolb, J., Tokovinin, A., Sarazin, M., A&A in press (2010) are used:

f(lambda[mu],z) = DIMM * (lambda / 0.5 ) ^ {-0.2} * z^{3/5}

factor=sqrt( 1-2.183 ( 0.98 * lambda[m] / L0 / f(lambda[mu],z) ) ^{0.356} )

dimm_corr = f( lambda[mu], z ) * factor( lambda[m] )

where lambda[mu] is the wavelength in microns, z is the air mass, L0 is the turbulence outer scale (L0=22m is used) and lambda[m] is the wavelength in m.

To compare the measured image quality with the image quality recorded by the optical CCD guider, only the wavelength is corrected when transforming to tel_guid_fwhm QC parameter into the tel_guid_fwhm_corr QC value.

The comparison between the photometric standard star IQ and the IQ reported by the autoguider is monitored here.

The comparison between the photometric standard star IQ and the DIMM is monitored here.


 
 
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