Open igorkolesnikov13 opened 1 year ago
Hi @igorkolesnikov13,
Hi @ebertin, thank you so much for the answer.
I was running some tests on galaxies from SDSS DR7. I found a pretty big difference between the Petrosian radius (Rp) provided by the SDSS catalog and that given by SExtractor (using default params, except for pixel scale). I used background subtracted and cleaned (without secondary objects) stamps as input.
To get the Rp in pixels from SExtractor, I used the formula for the area you provided earlier to get the area and then got the Rp with sqrt(area/pi).
I was wondering if you could point some direction for me to try to understand why there is such a difference, especially for elliptic galaxies.
Hi @igorkolesnikov13, this is quite puzzling. It works fine with spiral galaxies (except for glitches for some galaxies), so the formula seems right. Did you try to change (lower) the detection (and analysis) thresholds ? In SExtractor measurements always depend a bit on the detection threshold, as the scaling of the measurement window depends partly on the object footprint.
Hello, I'm using Sextractor to run some benchmarks on the code I'm working on. I'm mainly focused on Petrosial Radius (PETRO_RADIUS).
I have two main questions that I could not find in the documentation:
Thanks ahead for the help.