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HelloI am trying to use xregister to register dithered frames... The max off-set of any frame to the reference frame being used is about 15pixels in either x or y..
I have had to use xregister in several passes in order to get my images fully registered - that is to say although with each pass, xregister shifts my image in the right direction, it does not shift it far enough so I have to put this partially registered frame back into xregister so that it will get shifted a little closer , and so on until finally the image becomes registered.... the following lines of code will clarify what i mean:[code:1:fb35ca76ae]xregister ("@to_register.txt",
"ref_frame.fits", "[*,*]", "shifts1.db", output="@to_register.txt//_pass1", databasefmt=yes, append=no, records="",
coords="", xlag=0, ylag=0, dxlag=0, dylag=0, background="none", border=INDEF,
loreject=INDEF, hireject=INDEF, apodize=0., filter="none",
correlation="discrete", xwindow=11, ywindow=11, function="centroid", xcbox=10,
ycbox=10, interp_type="linear", boundary_typ="nearest", constant=0.,
interactive=no, verbose=yes, graphics="stdgraph", display="stdimage",
gcommands="", icommands="")xregister ("@to_register.txt//_pass1",
"ref_frame.fits", "[*,*]", "shifts2.db", output="@to_register.txt//_pass2", databasefmt=yes, append=no, records="",
coords="", xlag=0, ylag=0, dxlag=0, dylag=0, background="none", border=INDEF,
loreject=INDEF, hireject=INDEF, apodize=0., filter="none",
correlation="discrete", xwindow=11, ywindow=11, function="centroid", xcbox=10,
ycbox=10, interp_type="linear", boundary_typ="nearest", constant=0.,
interactive=no, verbose=yes, graphics="stdgraph", display="stdimage",
gcommands="", icommands="")xregister ("@to_register.txt_pass2",
"ref_frame.fits", "[*,*]", "shifts3.db", output="@to_register.txt//_pass3", databasefmt=yes, append=no, records="",
coords="", xlag=0, ylag=0, dxlag=0, dylag=0, background="none", border=INDEF,
loreject=INDEF, hireject=INDEF, apodize=0., filter="none",
correlation="discrete", xwindow=11, ywindow=11, function="centroid", xcbox=10,
ycbox=10, interp_type="linear", boundary_typ="nearest", constant=0.,
interactive=no, verbose=yes, graphics="stdgraph", display="stdimage",
gcommands="", icommands="")
#...... and so on until //_passi at which point the images will be registered
[/code:1:fb35ca76ae]and the parameters I used are those shown in the above code....
Could I alter parameters so that I only have to run frames through xregister one time?Also note, there is partial fringing in both the ref_image and images to be registered...the fringe pattern is the same in both the ref_image and the images to be registered... So I think one possible reason for the number of passes I had to use is that xregister was conflicted as to whether it should keep the fringe pattern aligned or shift everything so that the astronomical objects are aligned instead....but I recall trying to use xregister on non-fringed images and I think the problem of needing several passes happened there too..
Final point: The quality of the registered images is significantly degraded from those of the initial images and this time I suspect that the fact that there was a fringe pattern may have caused this.....comments on all the points raised above are appreciated

I had pretty good luck with increasing the window size to allow for one pass, but I would specify a small region that I was interested in aligning. Maybe that would help?

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Rob Steele (Robert.D.Steele@jpl.nasa.gov)