CNSHD548725 Fwd from User: Bug in polimplot

[Guest]

Dear Doug,
I was forwarded your request via IRAF help and STScI help. I wrote the
imaging polarimetry tasks in the stecf.impol package.

I looked at your images. They had some floating overflow values in them
(- and + 3.38E38) which I am sure caused the automatic scaling in polimplot
to fail. I replaced these values and looked again. The StokesP.fits image
does not seem to have sensible values - there are many negative values which
doesnt make sense for polarization (it is supoposed to be in %, always
positive). The StokesA.fits has a centrosymmetric pattern of position angles
(it looks like a model to me). However the values go from -1.57 to +1.57
(neglecting a band of funnies across the middle of the image). polimplot
expects position angles in degrees. I multipled the PA image by 57.296
(after replacing the large positive and negative values) and when I
substituted
a flat polarization map (30%) got a centro symmetric pattern of vectors when
plotting so:

polimplot inpol="rubpol2.fits" inpopa="rubpa2.fits" poi_err=no inpoer=""
inpaer="" \
xybin=1 poscal=0.80 polow=1.0 pohigh=100.0 pacorr=0.0 xysam=9 polab=no
title="" xlabel="" \
ylabel="" device="stdgraph" left=0.3402 right=0.6598 bottom=0.3402 top=0.6598
erase=yes

I hope this helps. You can consult the web pages on this package at:
http://www.stecf.org/software/stecf-iraf/impol/index.html
There is a directory of demos which can be downloaded.

Please let me know if you need more assistance.

Cheers
Jeremy

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