QC PLOTS
DOME:	CURRENT	HISTORY
dome raw u_SDSS
dome raw g_SDSS
dome raw r_SDSS
dome raw i_SDSS
dome raw z_SDSS
dome raw B_JOHN
dome raw V_JOHN
master dome flat level
number of cold pixels
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.

During normal VST/OmegaCAM operations DOME flat frames are taken for each filter for which science data was obtained, and generally have a validity range of 4 days. They are usually obtained during day-time calibration and consist of 5 input, screen flat exposures (each with a flux level of about 20,000 ADU or more). The pipeline applies a bias-correction, trims the images, and then averages them together with a 5 sigma rejection of outliers (intended to reduce photon shot noise and to remove cosmic rays).

The pipeline creates two output frames from its dome flat recipe (omega_mdome): a master dome flat (OC_MFLD_<date>_1_1_normal_normal_<filter>.fits) and a cold pixel mask (OC_MCPM_<date>_1_1_normal_normal_<filter>.fits).

An OmegaCAM master dome flat (single detector).

An OmegaCAM master cold pixel map (single detector). A value of 1 indicates a cold pixels; otherwise 0.

QC1 Health Check Plots

The QC1 health check plots for the RAW OmegaCAM dome flats are divided into 7 separate linked pages, each of which shows the trending for each of 7 different filters. Since the master dome flat produced by the OmegaCAM pipeline is normalized, it is not easy to detect whether or not one of the input dome flat frames was either saturated or had insufficient flux. For this reason, the raw dome flat parameters are monitored. A further set of QC1 health check plots exist for the OmegaCAM master dome flats monitoring both the level and the number of detected cold pixels.

• for each of the filters: u_SDSS, g_SDSS, r_SDSS, i_SDSS, z_SDSS, B_JOHN, and V_JOHN:
  • raw dome flats median level averaged over all 32 detectors
  • raw dome flat median level for each detector
  • raw dome minimum and maximum level averaged over all 32 detectors
  • score outliers
    
    
• for ALL filters (possible since the master dome flats are normalized):
  • master dome flat median level averaged over all 32 detectors
  • master dome flat median level for each detector
  • master dome flat rms averaged over all 32 detectors
  • score outliers
  • number of cold pixels averaged over all 32 detectors
  • number of cold pixels for each detector
  • score outliers

QC1 parameters (trended for each individual detector)

QC Reports for DOME flat frames

QC Report 1:
left: full-field image of the master dome flat of the extension listed at the top of the image
center left: 4x zoom of the center area of the master dome flat
center right: the difference of the reference master dome flat and the current master dome flat frames The median level of the difference image is listed to the right of the frame
right: full-field image of the cold pixels map. The positions of the reference frame cold pixels are shown in red, while the cold pixels of the current dome flat frame are shown in blue.
The total numbers of cold pixels are listed in the frame legend.

QC Report 2:
top left: a) three single column traces of the current and reference master dome flats through:
x = 256 (dark grey)
x = 1024 (middle grey)
x = 1792 (light grey)
b) average of all columns (normalized) of current master dome flat (thick blue line)
c) average of all columns (normalized) of reference master dome flat (thick red line)
top center: a) three single row traces of the current and reference master dome flats through:
y = 256 (dark grey)
y = 2048 (middle grey)
y = 3840 (light grey)
b) average of all rows (normalized) of current master dome flat (thick blue line)
c) average of all rows (normalized) of reference master dome flat (thick red line)
top right: a) logarithmic histogram of current master dome flat (blue line)
b) logarithmic histogram of reference master dome flat (red line)
The median levels (as computed from a Gaussian fit) are shown as vertical dashed lines and listed in the legend
lower left: difference between the average column traces of the reference and current master dome flat frames
lower center: difference between the average row traces of the reference and current master dome flat frames In both plots, the zero line is shown in orange as a reference.
lower right: logarithmic histogram of the difference between the reference and current master dome flat frames. Ideally, the histogram should straddle the zero line (shown in orange).
The median difference (as computed from a Gaussian fit) is shown as vertical dashed green line.

QC Report 3:
left: full-field image of the first raw dome flat executed in the template
center: full-field image of the last raw dome flat executed in the template
top right: a) six single column traces of the current raw dome flats through:
x = 256 (dark grey) for the first and last raw domes
x = 1024 (middle grey) for the first and last raw domes
x = 1792 (light grey) for the first and last raw domes
b) average of all columns of the first raw dome flat (thick red line)
c) average of all columns of the last raw dome flat (thick blue line)
bottom right: a) six single row traces of the current raw dome flats through:
x = 256 (dark grey) for the first and last raw domes
x = 1024 (middle grey) for the first and last raw domes
x = 1792 (light grey) for the first and last raw domes
b) average of all rows of the first raw dome flat (thick red line)
c) average of all rows of the last raw dome flat (thick blue line)

Trending and Issues

Since the master dome flat produced by the OmegaCAM pipeline is normalized, it is not easy to detect whether or not one of the input dome flat frames was either saturated or had insufficient flux. For this reason, the raw dome flat statistics are monitored. QC report #3 will clearly show a saturated raw dome, or a raw dome with too little flux. Both parameters are monitored and scored.

All saturated dome flats are rejected and reported to Paranal.

Occasionally it may also happen that dome flat flux levels are very low (i.e. <1000 ADU). The source of this may be that the M1 covers were in place during the exposure, or that the dome flat lamp was not turned on. These dome flats are also rejected and reported to Paranal.
Finally, since the dome flat lamp is very red, the dome flats made with the u_SDSS, the u-band quadrant of the u_g_r_i_SDSS, and even the B_JOHN filters can have very low flux levels. This has to be tolerated as there is no alternative dome flat lamp.

History

OmegaCAM DOME flats tend to be very stable.