QC PLOTS
	CURRENT	HISTORY
MOS efficiency
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.

Spectrophotometric standard stars are observed for all grisms dependent on the usage of the settings for science. Their purpose is to monitor the overall instrument efficiency (telescope+instrument+detector) and to provide a measure of the spectral response. In MOS mode, standard stars are observed with dedicated masks having eight slits where the standard star is present in one of them.

Information about response curves and flux calibration can be found here. MOS observations of standards can suffer from slit losses. An example is provided here.

The VIMOS pipeline extracts the signal of the standard star in the same way as for science observations. Then, the efficiency curve is calculated as the ratio of the observed flux (in e-/sec/A) at airmass one and the catalog flux of the star (converted to the expected number of electrons). The response is the ratio of the catalog flux to the observed flux (for airmass one). For the purpose of Quality Control, the efficiency is resampled at 15 fixed wavelengths from 3700A to 9300A with 400A step size.

QC1 parameters

Trending

For each grism, one QC1 efficiency parameter is monitored over time as a measure for the time dependency of the overall efficiency in each setting. The following associations are used:

In addition to the trending over time, an overview plot showing the spectral distribution of the efficiency for all wavelengths is also available. Standard star measurements from 1 September 2005 to 30 June 2006 have been evaluated and averaged for this purpose.