AIPS HELP file for OVRSWTCH in 31DEC26

As of Sat Jan 24 11:18:34 2026

HELP SECTION

OVRSWTCH
Type: Adverb  (scalar)
Use:  To specify when OVERLAP >= 2 mode is changed to OVERLAP = 1 mode
      while Cleaning single-Gaussian, multi-facet images in IMAGR.
      The mode is switched when the peak residual reaches
      abs(OVRSWTCH) Jy/beam.  If OVRSWTCH < 0, ONEBEAM is changed to
      TRUE for the OVERLAP = 1 portion of the Clean.

Null value: 0.0
      Do not switch modes

Tasks:
   IMAGR.........Fourier transforms and Cleans uv data with wide-field,
                 interactive TV, and data weighting options.
                 In OVERLAP=2 mode, AIPS images all facets to begin with
                 and then Cleans only one.  It subtracts the components
                 from the residual uv data, chooses another facet,
                 images it with the new residual data, Cleans it, and so
                 forth.  This has the desirable attribute of avoiding
                 the sidelobes of the strong sources as they might
                 appear in other facets because they are subtracted
                 before those facets are imaged and Cleaned.  OVERLAP=1
                 mode images all facets at once, Cleans them all, then
                 subtracts any components found in all factes from the
                 residual uv data, and then re-images and Cleans all
                 facets again.  It may be appropriate to start in
                 OVERLAP=2 mode until the highest dynamic range
                 structures are removed and then, when the Cleaning gets
                 down near the noise levels, switch to OVERLAP=1 mode
                 for the last portion of the Clean.  OVRSWTCH is used to
                 define the residual brightness level at which this
                 switch will occur.
Procedures:
   LINIMAGE......Build image cube from multi-IF data set
                 OVRSWTCH sent to IMAGR
   TDSTEP3.......Time-dependent imaging procedure "step 3"
                 OVRSWTCH sent to IMAGR

EXPLAIN SECTION