Evolution of the Response Function

The Response Function (RF) is computed during (photometric) technical or calibration nights. For this purpose spectrophotometric standars are observed with Grism 11 and a slit of 5". Because EFOSC2 uses an UV-flooded CCD, it is important to monitor the response in the blue region of the spectrum.

The figure below shows RFs computed in different dates.

Notes:

• February 2010: standars where observed with the two off-centered slits, so the blue and red curves show the gain in spectral coverage that can be obtained with this method.
• First half of 2010: the ca. 24% lower response is due to dust accumulating on the main mirror of the NTT. After mirror washing the system efficiency has been restored (see 2010-dec-21).
• February 2012: dust is again progressively reducing the system efficiency, as ZPs in QC pages confirm.
• December 2012: response is ca. 9% less than the best recorded.
• General: For a finer time sampling of the efficiency evolution, the zero-points computed by the pipeline can be inspected at the following link:
  Quality Control .