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Name

ccdstack - stack images, with simple gridding option if WCS differs

Synopsis

ccdstack [parameter=value]

Description

ccdstat stacks images and takes their mean, allowing for the WCS to be different. The current re-sampling method is simple: the first image inherits the WCS for the output stacked image, all other images compute in which pixel of the first image this pixel would contribute. No other gridding or convolution is done yet (but probably should).

Parameters

The following parameters are recognized in any order if the keyword is also given:
in=
Input image files, first image sets the WCS.
out=
Output image file. No default.
weight=
Scalar weight per image [1 for all].
sigma=
Are the weights still SIGMA (t), or straight
bad=
Bad value to ignore [0]
wcs=t|f
Use the WCS to re-sample for stacking with the WCS of the first image. If not set, images are stacked "as is". If WCS is set, you can thus stack images of unequal size. Pixels falling outside that of the first image are simply ignored. [Default: t]
fwhm=
If given, these are the convolution FWHM kernels in each dimension of the input images. It only makes sense to use this is wcs=t is used. Not Implemented Yet.
flux=0|1
Conserve flux (1) or not (0) in each dimension. Not implemented yet.

Examples

Since the first image determines the WCS of the output image, it can be also be used as a template by setting its image values to 0. ccdgen(1NEMO) can be used for this.

Here is a contrived example of mosaicing two fields in a Plummer sphere projection. It will generate a template with all 0 values (which don’t contribute to the stack), and adding in the two fields: 

    mkplummer p1 100000
    snapgrid p1 ccd1 xrange=0:1 yrange=0:1    nx=16 ny=16
    snapgrid p1 ccd2 xrange=-1:0 yrange=-1:0  nx=16 ny=16
    ccdgen "" ccd3 spar=0 size=64,64 cdelt=4/64,4/64
    ccdstack ccd3,ccd1,ccd2 ccd12
    ccdstack ccd3,ccd2,ccd1 ccd21

See Also

ccdmoms(1NEMO) , rvstack(1NEMO) , ccdmath(1NEMO) , ccdborder(1NEMO) , ccdgen(1NEMO) , image(5NEMO)

Files

src/image/misc

Author

Peter Teuben

Update History


21-May-21    V0.1 Drafted    PJT

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