7C. MSCstack

Mscstack takes the geometrically transformed images, and "stacks" them into a single image per filter, using the values of mscscale and msczero that have been entered into the image headers by "philmatch" as intensity scaling and offset values. It also allows us to create a bad pixel mask.


PACKAGE = mscred
   TASK = mscstack

input   =                  @us  List of images to combine
output  =          N6822U.fits  Output image
(headers=                     ) List of header files (optional)
(bpmasks=               n6822u) List of bad pixel masks (optional)
(rejmask=                     ) List of rejection masks (optional)
(nrejmas=                     ) List of number rejected masks (optional)
(expmask=                     ) List of exposure masks (optional)
(sigmas =                     ) List of sigma images (optional)

(combine=              average) Type of combine operation (median|average)
(reject =              ccdclip) Type of rejection
(masktyp=            goodvalue) Mask type
(maskval=                   0.) Mask value
(blank  =               50000.) Value if there are no pixels

(scale  =            !mscscale) Image scaling
(zero   =             !msczero) Image zero point offset
(weight =                 none) Image weights
(statsec=                     ) Image section for computing statistics

(lthresh=                   1.) Lower threshold
(hthresh=                INDEF) Upper threshold
(nlow   =                    1) minmax: Number of low pixels to reject
(nhigh  =                    1) minmax: Number of high pixels to reject
(nkeep  =                    1) Minimum to keep (pos) or maximum to reject (neg)
(mclip  =                  yes) Use median in sigma clipping algorithms?
(lsigma =                   3.) Lower sigma clipping factor
(hsigma =                   3.) Upper sigma clipping factor
(rdnoise=                   10) ccdclip: CCD readout noise (electrons)
(gain   =                  2.2) ccdclip: CCD gain (electrons/DN)
(snoise =                    0) ccdclip: Sensitivity noise (fraction)
(sigscal=                  0.1) Tolerance for sigma clipping scaling corrections
(pclip  =                 -0.5) pclip: Percentile clipping parameter
(grow   =                   0.) Radius (pixels) for neighbor rejection
(mode   =                   ql)

In order to run it on a bunch of images, we execute a little script that looks something like this:


mscstack @us WLMU.fits bpmask=wlmu
mscstack @bs WLMB.fits bpmask=wlmb
mscstack @vs WLMV.fits bpmask=wlmv
mscstack @rs WLMR.fits bpmask=wlmr
mscstack @is WLMI.fits bpmask=wlmi
mscstack @has WLMHA.fits bpmask=wlmha
mscstack @s2s WLMS2.fits bpmask=wlms2
mscstack @o3s WLMO3.fits bpmask=wlmo3
delete dstack
files WLM*.fits > dstack
philtrans dstack dstack WLMU
This last step is kind of dangerous: we shift the stacked images, replacing the existing ones, so that they all line up. See the next section for more.