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| QC PLOTS |
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CURRENT |
HISTORY |
| Bias level, RON |
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| 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. |
2008-05-24: new GIRAFFE CCD "Carreras" operational
(replacing "Bruce"), find documentation for the old and the new CCD here.
Both CCDs are identical in format and size; unless otherwise specified,
the content below applies to both CCDs.
A set of 5 BIAS frames is measured daily as part of the routine calibration
and health check plan. The BIAS level, the read noise and the structure are monitored.
Other CCD parameters are monitored using the darks and the image
flats.
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BIAS frame.
There is an upward gradient of the order of several ADU which is monitored by
the STRUCTY parameter. The bright vertical feature is a bad column. |
Find other detector parameters documented here:
| dark parameters |
dark |
| detector parameters like gain, contamination etc. |
detector |
Box 1 shows the mean BIAS level measured across the whole CCD, given in
ADU.
QC1 parameters
| parameter |
QC1 database: table, name |
procedure |
| "BIAS_level": median of bias level |
giraffe_bias..median_master |
median of whole master_bias; values below 100 and above 300 ADU
are clipped |
Trending
The median bias level is plotted in box 1 of the trending
plot.
History
There is a trending plot covering the full history of contamination
(here). The mean
bias has slowly decreased over the years.
The read noise (RON) is measured as rms in a single raw frame
and in the master bias frame, using in both cases a small central window 100x100
pixels wide. The RON of the master bias frame is about a factor sqrt(N) lower than
the raw file RON, where N typically is 5. RON is given in electrons, calculated from
the ADU value using the nominal transformation factor (CONAD = 1/gain) 2.25
e-/ADU. (The measured CONAD values are close to that value, check out here.)
QC1 parameters
| parameter |
QC1 database: table, name |
procedure |
| RON (raw) |
giraffe_bias..sigma_raw |
measures rms in a single raw frame (the first one), using
a small central window 100x100 pixels wide; clip outliers below 100 and above
300 ADU |
| RON (master) |
giraffe_bias..sigma_master |
same, for the master bias frame |
Trending
Box 2 of the trending
plot shows the RON of single raw BIAS frames, box 3 the RON of master
bias frames.
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RON plots. Box 2 shows the RON of
single raw BIAS frames, box 3 the RON of master bias frames, typically constructed
from 5 input raw frames.
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The GIRAFFE BIAS frames contain some structure which is monitored here.
QC1 parameters
| parameter |
QC1 database: table, name |
procedure |
| "STRUCT_X": structure in X direction (rows) |
giraffe_bias..struct_row |
collapse the master_bias in Y direction, measure rms of result
frame |
| "STRUCT_Y": structure in Y direction (columns) |
giraffe_bias..struct_col |
same, in X direction |
Trending
Box 4 and 5 of the trending
plot show the structure of the BIAS, derived from collapses
of columns (structure in X direction, left) and rows (Y direction, right).
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Structure plots. The structure in X direction is derived
in the master bias, collapsed along the rows (box
4). The structure in Y is obtained along the columns (box 5). The collapses
are shown below.
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Collapsed master bias. While
the master bias has virtually no structure in X direction (along the rows), it
is quite structured vertically (along the columns). Roughly the first 1000 rows
increase from a level about 4 ADU below average to the average level. The step
is due to the bad columns around column 420 starting at about row 1460. |
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