STACKER

Name

stacker

Purpose (one Line Only)

Stack (co-add) image while registering images.

Description

Calling Sequence

stacker,fnlist,xpos,ypos,image

Inputs

fnlist - String array of fits files to read, or, 3-d image array, for
the raw images to be stacked.
xpos - Array of x-positions, one per frame of registration point.
ypos - Array of y-positions, one per frame of registration point.

Optional Input Parameters

Keyword Input Parameters

ANCHORFRAME - Index into fnlist for the frame to be used as the anchor.
Default is the first frame.
ANCHORPOS - [x,y] position to align registration point to, default is
the position of the anchor object.
BAD - If specified, String array of fits files to read, or, 3-d image
array, for badmasks applying to the raw images to be stacked.
CROP - [x1,x2,y1,y2] region of image to save. These values are
in the pixel coordinate system of the anchor frame.
Default is the full frame.
EXTENSION - Image extension to read from image fits files. This should be
left off if the file is not a group fits file. If it
is a group fits file you will need to specify this number
to get the right extension.
JUSTMEDIAN - Only use median combination in avgclip call.
LAYER - 2-d subframe to read from image fits files. This should be
left off if the files are 2-d fits files. If they
are 3-d cubes you will need to specify this number
to get the right part of the image. This applies ONLY
to IMAGE fits files- BAD mask files are always 2-d.
JUSTMEDIAN - Only use median combination in avgclip call (ie if ROBUST
keyword in force).
NTOPCLIP - (default=0) How many of the brightest pixels to removed
before the robust statistics. (see medarr_mwb.pro)
ROBUST - Flag, if set requests that a robust average, via avgclip,
of the image stack be performed. If the number of images is
2 then this keyword is ignored.
SILENT - Flag, if set will suppress all messages to screen.
SUPERFRAME- Flag, if set, the images will be stacked onto a
'superframe' which is sufficiently large so that all
pixels in the individual images will be represented at
least once. A special badmask is used to mask off unpopulated
elements of the supercube being stacked.
DEBUG - Flag, if set turns on extra debug steps and other information.
The debug information in not guaranteed to remain static
from one verion of the program or another.

Outputs

image - Floating point array with stacked image

Keyword Output Parameters

OUTFILE - Name of file to write the image to. This is output in FITS format
and the header is derived from the first image with some
modifications.
IMAGESTACK - use this to get the registered stack of individual frames
STACKOFFSET- a 2 x n matrix giving the X,Y offsets of each individual
frame in the stacked image. That is, stackoffset[*,j]
are the X,Y for the lower left corner of the jth frame
on the stacked image. Depending on the setting of
SUPERFRAME and the explicit cropping parameters, this
may not be located within the dimensions of the stacked
image.
STACKSIZE- a 2 element long vector giving the X,Y dimensions of the
output stack and output image. In the absence of CROP and
SUPERFRAME keywords this will be the dimensions of the anchor
frame.
IMAGEMEAN - This is the mean of the output image background signal level
as computed and used inside this routine.

Common Blocks

Side Effects

Restrictions

Procedure

Modification History

Written by Marc W. Buie, Lowell Observatory, 2005/07/21
2005/11/22, MWB, added DEBUG keyword
2006/10/20, MWB, fixed missing keyword problems
2007/07/09, MWB, added JUSTMEDIAN and STACK keywords
2007/08/30, Peter L. Collins, Lowell Observatory, allow data cube as
variant of fnlist, and fits file as variant of BAD. Add
SUPERFRAME support and associated keywords.
2007/09/07, MWB, incorporate into library to be consistent with newest
avgclip and medarr_mwb, STACK keyword renamed to IMAGESTACK
2012/12/16, MWB, added NTOPCLIP keyword