https://casaguides.nrao.edu/index.php?title=VLBA_Basic_Phase-referencing_Calibration_and_Imaging&feed=atom&action=historyVLBA Basic Phase-referencing Calibration and Imaging - Revision history2024-03-28T17:39:19ZRevision history for this page on the wikiMediaWiki 1.38.6https://casaguides.nrao.edu/index.php?title=VLBA_Basic_Phase-referencing_Calibration_and_Imaging&diff=35453&oldid=prevJlinford: /* Creating the Measurement Set */2023-09-26T16:26:10Z<p><span dir="auto"><span class="autocomment">Creating the Measurement Set</span></span></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 12:26, 26 September 2023</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l103">Line 103:</td>
<td colspan="2" class="diff-lineno">Line 103:</td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div></source></div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div></source></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The ''scanreindexgap_s'' parameter is used to reconstruct scan boundaries in those cases where sources do not change between scans. In general, it is good to set ''scanreindexgap_s'' to some non-zero number to help CASA properly organize the scan list. The recommended value is 15, but shorter values may work as well (although you probably don't want to go much shorter than about 5 seconds). If you find that the resulting MS contains too few scans, run [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casatasks.data.importfitsidi.html importfitsidi] again with ''scanreindexgap_s'' set to a smaller number. If your MS has too many scans, especially multiple scans on the same source when you think it should just be one scan, run [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casatasks.data.importfitsidi.html importfitsidi] again with ''scanreindexgap_s'' set to a larger number.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The ''scanreindexgap_s'' parameter is used to reconstruct scan boundaries in those cases where sources do not change between scans. In general, it is good to set ''scanreindexgap_s'' to some non-zero number to help CASA properly organize the scan list. The recommended value is 15 <ins style="font-weight: bold; text-decoration: none;">seconds</ins>, but shorter values may work as well (although you probably don't want to go much shorter than about 5 seconds). If you find that the resulting MS contains too few scans, run [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casatasks.data.importfitsidi.html importfitsidi] again with ''scanreindexgap_s'' set to a smaller number. If your MS has too many scans, especially multiple scans on the same source when you think it should just be one scan, run [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casatasks.data.importfitsidi.html importfitsidi] again with ''scanreindexgap_s'' set to a larger number.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><b> NOTE: </b>You may see warnings in the CASA window like "Table not yet implemented" and "Keyword has wrong data type". This is normal behavior for VLBA data and due to the fact that CASA does not yet handle the pulse-cal tone data in the FTIS-IDI file. Just ignore them. However, do not ignore any SEVERE <del style="font-weight: bold; text-decoration: none;">warngins</del>, as these can indicate there are serious problems with the data.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><b> NOTE: </b>You may see warnings in the CASA window like "Table not yet implemented" and "Keyword has wrong data type". This is normal behavior for VLBA data and due to the fact that CASA does not yet handle the pulse-cal tone data in the FTIS-IDI file. Just ignore them. However, do not ignore any SEVERE <ins style="font-weight: bold; text-decoration: none;">warnings</ins>, as these can indicate there are serious problems with the data.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Inspecting the Data ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Inspecting the Data ==</div></td></tr>
</table>Jlinfordhttps://casaguides.nrao.edu/index.php?title=VLBA_Basic_Phase-referencing_Calibration_and_Imaging&diff=35452&oldid=prevJlinford at 16:23, 26 September 20232023-09-26T16:23:05Z<p></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 12:23, 26 September 2023</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l105">Line 105:</td>
<td colspan="2" class="diff-lineno">Line 105:</td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The ''scanreindexgap_s'' parameter is used to reconstruct scan boundaries in those cases where sources do not change between scans. In general, it is good to set ''scanreindexgap_s'' to some non-zero number to help CASA properly organize the scan list. The recommended value is 15, but shorter values may work as well (although you probably don't want to go much shorter than about 5 seconds). If you find that the resulting MS contains too few scans, run [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casatasks.data.importfitsidi.html importfitsidi] again with ''scanreindexgap_s'' set to a smaller number. If your MS has too many scans, especially multiple scans on the same source when you think it should just be one scan, run [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casatasks.data.importfitsidi.html importfitsidi] again with ''scanreindexgap_s'' set to a larger number.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The ''scanreindexgap_s'' parameter is used to reconstruct scan boundaries in those cases where sources do not change between scans. In general, it is good to set ''scanreindexgap_s'' to some non-zero number to help CASA properly organize the scan list. The recommended value is 15, but shorter values may work as well (although you probably don't want to go much shorter than about 5 seconds). If you find that the resulting MS contains too few scans, run [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casatasks.data.importfitsidi.html importfitsidi] again with ''scanreindexgap_s'' set to a smaller number. If your MS has too many scans, especially multiple scans on the same source when you think it should just be one scan, run [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casatasks.data.importfitsidi.html importfitsidi] again with ''scanreindexgap_s'' set to a larger number.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><b> NOTE: </b>You may see warnings in the CASA window like "Table not yet implemented" and "Keyword has wrong data type". This is normal behavior for VLBA data and due to the fact that CASA does not yet handle the pulse-cal tone data in the FTIS-IDI file. Just ignore them.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><b> NOTE: </b>You may see warnings in the CASA window like "Table not yet implemented" and "Keyword has wrong data type". This is normal behavior for VLBA data and due to the fact that CASA does not yet handle the pulse-cal tone data in the FTIS-IDI file. Just ignore them<ins style="font-weight: bold; text-decoration: none;">. However, do not ignore any SEVERE warngins, as these can indicate there are serious problems with the data</ins>.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Inspecting the Data ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Inspecting the Data ==</div></td></tr>
</table>Jlinfordhttps://casaguides.nrao.edu/index.php?title=VLBA_Basic_Phase-referencing_Calibration_and_Imaging&diff=35130&oldid=prevJlinford at 20:39, 17 May 20232023-05-17T20:39:10Z<p></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 16:39, 17 May 2023</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l40">Line 40:</td>
<td colspan="2" class="diff-lineno">Line 40:</td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Alternatively, you may download the data from the [https://data.nrao.edu NRAO Archive]. In the archive search inputs, enter "TL016" in the Project Code field. Expand the results for TL016B and look for the file VLBA_TL016B_tl016b_BIN0_SRC0_1_220307T210851.idifits. Select the file, click "Download", and follow the instructions. Once you have downloaded the FITS-IDI file from the archive, it will be helpful to change the filename to "TL016B.idifits".</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Alternatively, you may download the data from the [https://data.nrao.edu NRAO Archive]. In the archive search inputs, enter "TL016" in the Project Code field. Expand the results for TL016B and look for the file VLBA_TL016B_tl016b_BIN0_SRC0_1_220307T210851.idifits. Select the file, click "Download", and follow the instructions. Once you have downloaded the FITS-IDI file from the archive, it will be helpful to change the filename to "TL016B.idifits".</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>== The <del style="font-weight: bold; text-decoration: none;">Observation </del>==</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>== The <ins style="font-weight: bold; text-decoration: none;">Observing Log </ins>==</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Before diving into the calibration, it is always a good idea to look over the observing log to check for notes from the operators that can inform us about potential issues with the data (missing stations, bad weather, etc.). These logs are always emailed to the PI's of an observation, but you can also access them later from the NRAO's [http://www.vlba.nrao.edu/astro/VOBS/astronomy/ vlbiobs fileserver]. To locate an observing log, first find the directory for observing month and the last two digits of the year (for the observation used in this Guide, that directory is [http://www.vlba.nrao.edu/astro/VOBS/astronomy/feb22/ feb22] for February 2022). Once inside the proper month+year directory, look for the project code (in this case, [http://www.vlba.nrao.edu/astro/VOBS/astronomy/feb22/tl016b/ tl016b]). Look for a file named <project code>log.vbla ([http://www.vlba.nrao.edu/astro/VOBS/astronomy/feb22/tl016b/tl016blog.vlba tl016blog.vlba]).</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Before diving into the calibration, it is always a good idea to look over the observing log to check for notes from the operators that can inform us about potential issues with the data (missing stations, bad weather, etc.). These logs are always emailed to the PI's of an observation, but you can also access them later from the NRAO's [http://www.vlba.nrao.edu/astro/VOBS/astronomy/ vlbiobs fileserver]. To locate an observing log, first find the directory for observing month and the last two digits of the year (for the observation used in this Guide, that directory is [http://www.vlba.nrao.edu/astro/VOBS/astronomy/feb22/ feb22] for February 2022). Once inside the proper month+year directory, look for the project code (in this case, [http://www.vlba.nrao.edu/astro/VOBS/astronomy/feb22/tl016b/ tl016b]). Look for a file named <project code>log.vbla ([http://www.vlba.nrao.edu/astro/VOBS/astronomy/feb22/tl016b/tl016blog.vlba tl016blog.vlba]).</div></td></tr>
</table>Jlinfordhttps://casaguides.nrao.edu/index.php?title=VLBA_Basic_Phase-referencing_Calibration_and_Imaging&diff=34957&oldid=prevJlinford at 15:20, 22 March 20232023-03-22T15:20:16Z<p></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 11:20, 22 March 2023</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l14">Line 14:</td>
<td colspan="2" class="diff-lineno">Line 14:</td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* Low Frequency (<4 GHz) &mdash; Total electron content (TEC) corrections have not yet been verified to work correctly for VLBI observations in CASA. Also, note that many C-band (4 to 8 GHz) VLBA observations will benefit from TEC corrections.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* Low Frequency (<4 GHz) &mdash; Total electron content (TEC) corrections have not yet been verified to work correctly for VLBI observations in CASA. Also, note that many C-band (4 to 8 GHz) VLBA observations will benefit from TEC corrections.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* VLBA+Y27 or other VLBA+ arrays that require the use of antab files &mdash; CASA does not currently support the use of antab files for ingesting calibration data (system temperatures, gain curves, etc.)</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* VLBA+Y27 or other VLBA+ arrays that require the use of antab files &mdash; CASA does not currently support the use of antab files for ingesting calibration data (system temperatures, gain curves, etc.)</div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">* VLBA data correlated prior to December 2009 &mdash; CASA cannot load data correlated with the old VLBA hardware correlator. Your data must have been correlated with the [https://go.nrao.edu/difx DiFX correlator].</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>If your observation involves any of the above, you should use [http://www.aips.nrao.edu/index.shtml AIPS] to calibrate your data.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>If your observation involves any of the above, you should use [http://www.aips.nrao.edu/index.shtml AIPS] to calibrate your data.</div></td></tr>
</table>Jlinfordhttps://casaguides.nrao.edu/index.php?title=VLBA_Basic_Phase-referencing_Calibration_and_Imaging&diff=33797&oldid=prevJlinford: /* Amplitude Self-Calibration */2023-01-03T17:55:02Z<p><span dir="auto"><span class="autocomment">Amplitude Self-Calibration</span></span></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 13:55, 3 January 2023</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l1132">Line 1,132:</td>
<td colspan="2" class="diff-lineno">Line 1,132:</td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Writing solutions to table: tl016b_cal1.apcal</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Writing solutions to table: tl016b_cal1.apcal</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div></pre></div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div></pre></div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The mean normalization factors are all close to 1.0, which is what we expect since we set ''solnorm=True''. If the mean values were far from 1.0, we would be worried that the amplitude self-calibration was not working properly (perhaps one or <del style="font-weight: bold; text-decoration: none;">more </del>antennas <del style="font-weight: bold; text-decoration: none;">was </del>drastically low or high).</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The mean normalization factors are all close to 1.0, which is what we expect since we set ''solnorm=True''. If the mean values were far from 1.0, we would be worried that the amplitude self-calibration was not working properly (perhaps one or <ins style="font-weight: bold; text-decoration: none;">two of the </ins>antennas <ins style="font-weight: bold; text-decoration: none;">were </ins>drastically low or high).</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>We should also take a look at the solutions on each telescope using [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casaplotms.plotms.html plotms].</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>We should also take a look at the solutions on each telescope using [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casaplotms.plotms.html plotms].</div></td></tr>
</table>Jlinfordhttps://casaguides.nrao.edu/index.php?title=VLBA_Basic_Phase-referencing_Calibration_and_Imaging&diff=33796&oldid=prevJlinford: /* Self-Calibration of Phase Reference Calibrator */2023-01-03T17:20:12Z<p><span dir="auto"><span class="autocomment">Self-Calibration of Phase Reference Calibrator</span></span></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 13:20, 3 January 2023</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l911">Line 911:</td>
<td colspan="2" class="diff-lineno">Line 911:</td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Despite our best efforts with the initial calibration, VLBA observations will almost always require additional steps to improve the calibration. Because the VLBA antennas are separated by such large distances, the phases may not be perfectly calibrated by fringe fitting alone. This is partly because each antenna may be looking through vastly different troposphere/ionosphere, and partly because the phase reference calibrators are rarely point sources on long baselines (and fringe-fitting usually assumes the calibrators are point sources on all baselines).</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Despite our best efforts with the initial calibration, VLBA observations will almost always require additional steps to improve the calibration. Because the VLBA antennas are separated by such large distances, the phases may not be perfectly calibrated by fringe fitting alone. This is partly because each antenna may be looking through vastly different troposphere/ionosphere, and partly because the phase reference calibrators are rarely point sources on long baselines (and fringe-fitting usually assumes the calibrators are point sources on all baselines).</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>We will improve the calibration using "self-calibration". The process of self-calibration involves building models of the sources, refining the calibration based on those models, and then repeating until you converge to a good solution. The models are created during the imaging process. Each iteration self-calibration should produce images with lower noise. </div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>We will improve the calibration using "self-calibration". The process of self-calibration involves building models of the sources, refining the calibration based on those models, and then repeating until you converge to a good solution. The models are created during the imaging process. Each iteration <ins style="font-weight: bold; text-decoration: none;">of </ins>self-calibration should produce images with lower noise. </div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Each time the noise is reduced, you may notice dimmer structures appear. This is where you need to be careful. Including an apparent structure in a model for self-calibration can "build in" features that are not real. A good rule of thumb is "if you can't self-calibrate a structure away, it is probably real". So, if you are uncertain whether a newly apparent component is real or not, first try to self-calibrate without including that component in the model. If it sticks around, it is probably a real structure and including it in the next model should further improve the calibration and lower the noise in the next image.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Each time the noise is reduced, you may notice dimmer structures appear. This is where you need to be careful. Including an apparent structure in a model for self-calibration can "build in" features that are not real. A good rule of thumb is "if you can't self-calibrate a structure away, it is probably real". So, if you are uncertain whether a newly apparent component is real or not, first try to self-calibrate without including that component in the model. If it sticks around, it is probably a real structure and including it in the next model should further improve the calibration and lower the noise in the next image.</div></td></tr>
</table>Jlinfordhttps://casaguides.nrao.edu/index.php?title=VLBA_Basic_Phase-referencing_Calibration_and_Imaging&diff=33795&oldid=prevJlinford: /* Bandpass Calibration */2023-01-03T17:15:57Z<p><span dir="auto"><span class="autocomment">Bandpass Calibration</span></span></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 13:15, 3 January 2023</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l845">Line 845:</td>
<td colspan="2" class="diff-lineno">Line 845:</td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The bands look pretty good, but there is some offset between the bands and between polarizations ("correlations") inside each band. This is usually not a big deal and can be corrected with self-calibration.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The bands look pretty good, but there is some offset between the bands and between polarizations ("correlations") inside each band. This is usually not a big deal and can be corrected with self-calibration.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The bandpass calibration often does not perfectly calibrate the channels at the beginning and end of each spectral window. We can see such problems in <del style="font-weight: bold; text-decoration: none;">out </del>data where there are often outliers (both high and low) at the edges of each band. It is often a good idea to get rid of the edge channels that are not well-calibrated. We will use [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casatasks.flagging.flagdata.html flagdata] to get rid of some of the edge channels.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The bandpass calibration often does not perfectly calibrate the channels at the beginning and end of each spectral window. We can see such problems in <ins style="font-weight: bold; text-decoration: none;">our </ins>data where there are often outliers (both high and low) at the edges of each band. It is often a good idea to get rid of the edge channels that are not well-calibrated. We will use [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casatasks.flagging.flagdata.html flagdata] to get rid of some of the edge channels.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>For our data, we will flag the first and last 3 channels of each spw.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>For our data, we will flag the first and last 3 channels of each spw.</div></td></tr>
</table>Jlinfordhttps://casaguides.nrao.edu/index.php?title=VLBA_Basic_Phase-referencing_Calibration_and_Imaging&diff=33794&oldid=prevJlinford: /* Bandpass Calibration */2023-01-03T17:14:44Z<p><span dir="auto"><span class="autocomment">Bandpass Calibration</span></span></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 13:14, 3 January 2023</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l837">Line 837:</td>
<td colspan="2" class="diff-lineno">Line 837:</td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>It will probably take a while for [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casatasks.calibration.applycal.html applycal] to run again, since you are also applying the solutions from the global fringe fitting.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>It will probably take a while for [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casatasks.calibration.applycal.html applycal] to run again, since you are also applying the solutions from the global fringe fitting.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>After <del style="font-weight: bold; text-decoration: none;">aplpying </del>the bandpass solutions, take a look at the calibrated data with [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casaplotms.plotms.html plotms].</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>After <ins style="font-weight: bold; text-decoration: none;">applying </ins>the bandpass solutions, take a look at the calibrated data with [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casaplotms.plotms.html plotms].</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div><source lang="python"></div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div><source lang="python"></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#In CASA</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#In CASA</div></td></tr>
</table>Jlinfordhttps://casaguides.nrao.edu/index.php?title=VLBA_Basic_Phase-referencing_Calibration_and_Imaging&diff=33452&oldid=prevJlinford: /* Self-Calibration of Phase Reference Calibrator */2022-11-10T22:53:48Z<p><span dir="auto"><span class="autocomment">Self-Calibration of Phase Reference Calibrator</span></span></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 18:53, 10 November 2022</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l1072">Line 1,072:</td>
<td colspan="2" class="diff-lineno">Line 1,072:</td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Notice that when refining both the delays and the phases we set ''minblperant=3'' because closure phases require at least 3 baselines.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Notice that when refining both the delays and the phases we set ''minblperant=3'' because closure phases require at least 3 baselines.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Apply the phase self-calibration <del style="font-weight: bold; text-decoration: none;">soultions </del>to the phase reference calibrator.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Apply the phase self-calibration <ins style="font-weight: bold; text-decoration: none;">solutions </ins>to the phase reference calibrator.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div><source lang="python"></div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div><source lang="python"></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#In CASA</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#In CASA</div></td></tr>
</table>Jlinfordhttps://casaguides.nrao.edu/index.php?title=VLBA_Basic_Phase-referencing_Calibration_and_Imaging&diff=33438&oldid=prevJlinford: /* Imaging the Calibrator */2022-11-09T17:45:27Z<p><span dir="auto"><span class="autocomment">Imaging the Calibrator</span></span></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 13:45, 9 November 2022</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l958">Line 958:</td>
<td colspan="2" class="diff-lineno">Line 958:</td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Setting ''interactive=True'' will allow us to define the areas where there is real flux from the source ("clean windows"). The value for ''niter'' needs to be large enough that we can go through enough clean iterations to recover most of the source flux. You can set ''niter'' to any arbitrarily large number (a few hundred should be plenty), but 1000 is an easy value to remember. Setting ''savemodel='modelcolumn' '' will save the model we create for the image to the model column of the measurement set so we can use it for self-calibration.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Setting ''interactive=True'' will allow us to define the areas where there is real flux from the source ("clean windows"). The value for ''niter'' needs to be large enough that we can go through enough clean iterations to recover most of the source flux. You can set ''niter'' to any arbitrarily large number (a few hundred should be plenty), but 1000 is an easy value to remember. Setting ''savemodel='modelcolumn' '' will save the model we create for the image to the model column of the measurement set so we can use it for self-calibration.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Running [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casatasks.imaging.tclean.html tclean] with ''interactive=True'' will open a new Viewer Display Panel where you can control the cleaning of the image. You should see that J1154+6022 is fairly point-like. Use the zoom tool to select the region <del style="font-weight: bold; text-decoration: none;">aruond </del>the source. Use the "polygon drawing" tool to draw a clean window around the source, excluding the stuff to the left and right of the bright source. Click on the "Continue deconvolution" button (the green circular arrow on the right). Check the residuals when the display updates. Stop cleaning when the area around the source looks noise-like. For example, if you notice positive and negative regions with similar magnitudes (e.g., +0.003 and -0.003) inside your clean window, that is probably a good time to stop cleaning. To stop the cleaning process, click the "stop deconvolving now" button (the red circle with the white "X"). It may take [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casatasks.imaging.tclean.html tclean] a while to finish and close.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Running [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casatasks.imaging.tclean.html tclean] with ''interactive=True'' will open a new Viewer Display Panel where you can control the cleaning of the image. You should see that J1154+6022 is fairly point-like. Use the zoom tool to select the region <ins style="font-weight: bold; text-decoration: none;">around </ins>the source. Use the "polygon drawing" tool to draw a clean window around the source, excluding the stuff to the left and right of the bright source. Click on the "Continue deconvolution" button (the green circular arrow on the right). Check the residuals when the display updates. Stop cleaning when the area around the source looks noise-like. For example, if you notice positive and negative regions with similar magnitudes (e.g., +0.003 and -0.003) inside your clean window, that is probably a good time to stop cleaning. To stop the cleaning process, click the "stop deconvolving now" button (the red circle with the white "X"). It may take [https://casadocs.readthedocs.io/en/v6.4.0/api/tt/casatasks.imaging.tclean.html tclean] a while to finish and close.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div><b>NOTE: </b>If you need to delete a clean window, select "Erase" at the far left of the green region in the GUI and draw a box around the clean window(s) you want to delete, then double click. Remember to select "Add" again to define new clean windows.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div><b>NOTE: </b>If you need to delete a clean window, select "Erase" at the far left of the green region in the GUI and draw a box around the clean window(s) you want to delete, then double click. Remember to select "Add" again to define new clean windows.</div></td></tr>
</table>Jlinford