QC PLOTS
	LAST	HISTORY
imaging lamps (since 2007-04-01)
QC1 database (advanced users): browse | plot
imaging lamps (until 2007-03-25)
QC1 database (advanced users): browse | plot
spectroscopic lamps
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.

QC1 parameters

• efficiency (QC1 database table fors1_scrflat_2CCD, column efficiency)
  This is the median signal of the first raw frame devided by exposure time. The median value is computed within a window 250x150 pixel chosen close to the gap region between the 2 CCDs to minimize the illumination gradient. This is only a nominal 'efficiency' actually measuring the stability of exposure level (influenced by e.g. aging of lamps etc.).

Trending

History

In the case of the old FORS1 CCD (until 2007-03-25) the efficiency was determined per read-out port.

QC1 parameters

• lamp flux (QC1 database table fors1_lamp_chk, column flux)
  This parameter is determined from a bias-subtracted calibration lamp exposure in LSS mode. After background subtraction the total signal is integrated and normalized by the exposure time and the total number of original CCD pixels (keeping into account possible binning). The background is evaluated from the available overscan regions.

Trending

For trending we use only data obtained with the 300V grism with the GG435 filter and a 1" slit, using the standard resolution collimator..

History

In the case of the old FORS1 CCD (until 2007-03-25) the background was calculated from the first 200 CCD columns for flat field exposures, while for arc lamp data a background map evaluated from regions without spectral lines was computed and subtracted. This method has been used erroneously also for the new CCD mosaic until 2008-09-01. The correction of this bug resulted in a jump in flux for some of the monitored lamps.