Flatten map before making SNR mask FLT.ZERO_SNR_HIPASS
"
flt.zero_snr"
to be based
on a copy of the SNR map that has been high-pass filtering to remove structures larger than the
number of arc-seconds given by flt.zero_snr_hipass. This will in general reduce the number of source
pixels in the mask. See also parameter "
flt.zero_snr_ffclean"
. [0.0]