skycalc -- photometrically align images


skycalc [flags] reference_image image(s)

diffima d false
error e false
inputtab t ""
ordabs -1
ordsky -1
prefix p b
ref false
verbose v 0


diffima = true
difference imaging around stars (circular area with radius 50) to extract absorption and sky
error = false
Use error images too. If false, the error images are created simply by using the sqrt of the images. Only if true error files are created
inputab = ""
Table with stars used for difference imaging.
ordabs = -1
order of absorption fitting: -2 averaging after clipping (using 1/3 of all stars), -1 median, 0 order 0, 1 order 1, ...
ordsky = -1
order of sky fitting: -2 averaging after clipping (using 1/3 of all stars), -1 median, 0 order 0, 1 order 1, ...<
prefix = "b"
prefix for the result file
ref = false
calculating the basis from the reference file first (time consuming!), the first file is used as reference image
verbose = 0
Verbose level. If verbose >= 1 the test files sky-*.fits are created. If verbose >= 2 the test files abs-*.fits, abs_dia-*.fits, sky_dia-*.fits are created. If verbose >= 3 the test files ref_new.fits, e.ref_new.fits, ima_new-*.fits, e.ima_new-*.fits, diff-*.fits are created. If verbose >= 4 the test files diff_bin-*.fits are created. If verbose >= 5 the test files ref_bin-*.fits, ima_bin-*.fits are created.


The task skycalc -d aligns images to a reference frame extracting the sky and absorption difference using difference imaging of stars.


Note that for the test files the coordinate Zeropoint is at (nx/2,ny/2)
binnned absorption frame: ref ~ res = abs * ima - sky

binnned absorption frame: ref ~ res = abs * ima - sky

equal abs-*.fits but with stars and their absorption marked

equal sky-*.fits but with stars and their sky marked

ref_new.fits, e.ref_new.fits
reference image after nan correction

ima_new-*.fits, e.ima_new-*.fits
images after nan correction

binned difference diff = ref - abs * ima - sky;

strongly binned difference

strongly binned reference

strongly binned image


skycalc -d --ref --ordabs 1 --ordsky 2 -e -t stars.tbl -v 2 -p new reference.fits image.fits

Task index
This task was implemented by A. Riffeser
Dokumentation maintained by A. Riffeser
This file was last time updated on 06 Jul 2005