HOW-TO Create a HotPixelMap

What is a hot pixel map?

Figure 1: BiasFrame containing several bad columns of hot pixels.

A hot pixel map is an image of so-called hot pixels in the CCD detector. Hot pixels are pixels which indicate high values despite not being illuminated. These pixels are detected in bias images because biases have an exposure time of 0 seconds; they are not illuminated. In Astro-WISE the HotPixelMap is derived from the BiasFrame. Hot pixels destroy the value of all pixels behind the broken pixel as charge is moved through it during the read-out process of the CCD. The result is a bad column (see Figure 1).

The HotPixelMap is a mask image: good pixels have a value of 1 and bad pixels a value of 0.

Making a hot pixel map

To derive a HotPixelMap, type in the following at the AWE prompt:

awe> # Example using distributed processing (all CCDs simultaneously)
awe> dpu.run('HotPixels', i='OMEGACAM', d='2014-04-28', C=1)

or

awe> # Example using a Task (single CCD)
awe> task = HotPixelsTask(instrument='OMEGACAM', date='2014-04-28',
                          chip='ESO_CCD_#77', commit=1)
awe> task.execute()