Project

General

Profile

18 Whisker from windowednon-windowed moments for Feb 2013 exposures from firstcut catalog

In the new firstcut catalog (Feb. 2013), the moments measured using weights are also included. I am including the whisker/R50 results for the r, i, z band below. Note that R50 measurement is independent of weight kernel

1. Whisker based on non-weighted moments (in sextractor, the weighted moments is under the name of *WIN)

2. Whisker based on weighted moments. The kernel size of the weight has fwhm = 2*R50. So, the measured quantities is the result of both image and the weight kernel. Clearly, the whisker is much smaller.

3. Whisker based on the corrected weighted moments. The corrected weighted moments are the weighted moments after the correction for the contribution from the weight kernel. So, this should be compariable to 1.

Next, I show the cross comparison of the whiskers from different methods, as shown by the names on the axis.

1. Whisker from non-weighted moments and from corrected weighted moments

2. Whisker from non-weighted moments and from non-corrected weighted moments

3. Whisker from corrected weighted moments and non-corrected weighted moments.

So, the corrected weighted moments gives slightly smaller whisker. It is a tricky issue to say which one we should use to compare with the spec, corrected weighted one? or non-weighted one. Need to further discussions.