VIRCAM
Quality Control:
Photometric Standard Stars |
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QC1 parameters
History The photometric zeropoint are derived from the observation of photometric standard star fields and are dependent on several hardware and software components. While the 2MASS catalogue of the same version is used through the live time of the instrument, other components changed and had an impact on the zeropoint values: A) The following hardware related interventions took place:
# # 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
#
# 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
# # 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
# # file VC_GPCT_091031.fits # extensions 2 # -------------------------------------------- # XTENSION 1 # Number of columns 9 # filter_name|atm_extcoef|mag_offset|coleq_columns| coleq_errcols| coleq_coefs|gal_extcoef|default_zp|default_zp_err Z| 0.050000| 0.000000| Jmag,Hmag| e_Jmag,e_Hmag| 2.025,-1.025| 0.370000| 0.000000| 0.000000 Y| 0.050000| 0.000000| Jmag,Hmag| e_Jmag,e_Hmag| 1.61,-0.61| 0.140000| 0.000000| 0.000000 J| 0.050000| 0.000000| Jmag,Hmag| e_Jmag,e_Hmag| 0.923,0.077| 0.010000| 0.000000| 0.000000 H| 0.050000| 0.000000| Jmag,Hmag| e_Jmag,e_Hmag| 0.032,0.968| 0.015000| 0.000000| 0.000000 Ks| 0.050000| 0.000000| Jmag,Kmag| e_Jmag,e_Kmag| 0.01,0.99| 0.005000| 0.000000| 0.000000 NB118| 0.050000| 0.000000| Jmag,Hmag| e_Jmag,e_Hmag| 1.10,-0.10| 0.010000| 0.000000| 0.000000 NB980| 0.050000| 0.000000| Jmag,Hmag| e_Jmag,e_Hmag| 1.68,-0.68| 0.140000| 0.000000| 0.000000 C) The following major pipeline upgrades took place.
Independent on the used catalogue, the optical system (the telescope) and the atmosphere (seeing) affect the quality of the image shape of an extraterrestrial 'point source'. In bad seeing nights, the FWHM of the point source images on the detector and the shape of the point spread function are dominated by the turbulence in the atmosphere. In good seeing nights, when the seeing is small enough, the contribution of the optical system, the image quality of the telescope and the instrument become more and more apparent. Two parameters are derived from the standard stars observations: QC1 parameters
The VISTA telescope control software writes the coordinate system of the sky, the pointing direction, as world coordinates (ZPN projection) into the headers of the fits frames. In each detector extension the same RA and DEC (CRVAL1,2) values and the detector specific reference pixel (CRPIX1,2). The error between the real coordinates and the header coordinates, called pointing error is monitored. Is is a property/quality of the raw frame. QC1 parameters
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