ALCHEMI Data Reduction Group: Automasking


TIP Last Modified: JeffMangum - 06 September 2018

Table of Contents:

Issue

Auto-mask in tclean (auto-multithresh) sometimes sets clean masks on sidelobes. This happens most frequently for Band 7 imaging with 12m-only data (see example image below.) This example used the automask parameters that are recommended in Automasking CASA Guides (https://casaguides.nrao.edu/index.php/Automasking_Guide), namely sidelobethreshold=2.0, noisethreshold=4.25, minbeamfrac=0.3, and lownoisethreshold=1.5 for cleaing to 2sigma.

Update [2018-10-27]. This problem still occurs in CASA 5.4. Automasking in CASA 5.4 makes virtually the same mask as shown in the attached image made with CASA 5.3. One has to either adjust the automasking parameters or add a manual mask to constrain the area for auto-masking.

Task

Find a better set of parameters to avoid masking on sidelobes.

Current Status

-- JeffMangum - 2018-09-06
  • unsuccessful auto-mask:
    ngc253.B7j.12m.344500.nocontsub.image.ch55.png
Topic revision: r3 - 2018-10-27, KazushiSakamoto
This site is powered by FoswikiCopyright © by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding NRAO Public Wiki? Send feedback