AIPS HELP file for MAXPIXEL in 31DEC18
As of Mon Mar 19 22:12:53 2018
Type: Adverb (scalar)
Use: Specifies the maximum number of pixels to be searched
for Clean components during each major cycle of the Clark
version of Clean.
Null Value: 0 => 20050.
MX.......Make and deconvolve images from calibrated single-
source UV data files.
SDCLN....Deconvolve images, switching to Steer-Dewdnet-Ito
algorithm after a while.
AIPS Clean algorithm was designed by Barry Clark and modified
by Bill Cotton. In it, a certain number of the highest
pixels in the residual image is loaded to the "AP" memory to
be searched for components during each major cycle. The
performance and the results of the clean depend a lot on how
many pixels are searched. If too few are searched, then each
cycle will find only a few components and there will have to
be many (expensive) major cycles. If too many are searched,
then the algorithm wastes a lot of time searching and
subtracting from pixels it does not ever need. Also, when a
large number are searched, a larger beam patch is needed to
avoid making too much error inside the cycle. Use this
option sparingly, but values like 25000 or 30000 are found to
speed cleans of large images that develop many approximately
equal pixels in the residual image.