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If the convolved source is about the size of the beam along the major axis but slightly fatter along the minor axis then the deconvolution could move the PA by 90. Try IMFIT and/or JMFIT on the images. They do a correct deconvolution (of Gaussians) and they
try the fit values and plus/minus 1 sigma to make a matrix of deconvolved values. This should help to determine the reliability of the deconvolution.</div>
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Eric Greisen</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Daip <daip-bounces@listmgr.nrao.edu> on behalf of Hanno Spreeuw via Daip <daip@listmgr.nrao.edu><br>
<b>Sent:</b> Thursday, October 16, 2025 7:16 AM<br>
<b>To:</b> daip <daip@nrao.edu><br>
<b>Subject:</b> [daip] Question about DECONV.FOR {External}</font>
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<div>Hello,<br>
<br>
I have been running DECONV.FOR for some time and its output always seemed fine.<br>
I guess the current version - 31DEC25/APL/SUB/DECONV.FOR - does not differ from the previous ones.<br>
<br>
<b>Yet, I am a bit confused about its output when the convolved source is aligned with the restoring beam.</b><br>
<u>Then the returned, i.e. deconvolved, position angle is 90° larger than those position angles.</u><br>
<br>
E.g. <br>
<i>deconv(7.1941910149411346, 6.826481869094818, 86.02929942633546, 5.699093590220353, 4.181319049159876, 86.7612722265415)</i><br>
returns <br>
<i>(5.396174907684326, 4.390378952026367, 177.1446533203125, 0)<br>
</i>So rpa=<i>177.1446533203125</i> is 90° larger than one would expect.<br>
Could you please help me to explain this?<br>
<br>
Kind regards,<br>
Hanno Spreeuw<br>
<br>
PS To reproduce using Python, see the attached source file, which is the original DECONV.FOR with a few additions for f2py.<br>
<i>python -m numpy.f2py -c DECONV.FOR -m deconv_python<br>
ipython<br>
import numpy as np<br>
import deconv_python<br>
# print(deconv_python.deconv.__doc__)<br>
deconv_python.deconv(7.1941910149411346, 6.826481869094818, 86.02929942633546, 5.699093590220353, 4.181319049159876, 86.7612722265415)<br>
---> (5.396174907684326, 4.390378952026367, 177.1446533203125, 0)</i><br>
<br>
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