QACD-quack

TUTORIAL:

Filter and Normalise Data

1. Select Action | Filter and Normalise… from the menu.

2. There are two filtering options: clipping pixel totals and 3x3 median filter. By default both are selected. Leave them both selected and click OK.

3. A progress bar is displayed whilst the filtering and normalisation are performed. When completed, six more tabs will appear on the left hand side; only the first two (Filtered and Normalised) contain anything, the other three are initially empty.

4. Click on an element in the Filtered tab. There are white regions corresponding to invalid pixels, i.e. pixels that have been removed by the filtering process. The list of filtered elements includes a Total.

5. Click on an element in the Normalised tab. A normalised element map is the corresponding filtered element map divided by the total filtered map, and hence each pixel is in the range 0 to 1. There is no Total in the Normalised tab as all valid pixels would be 1. There is however an h-factor which is a weighting used when calculating ratios.