Recent changes to MakingImageCubes

MakingImageCubes modified by André Offringa

André Offringa — Tue, 25 Feb 2020 15:36:45 -0000

--- v7
+++ v8
@@ -9,7 +9,7 @@

 This will output 100 images, named wsclean-0000-image.fits, wsclean-0001-image.fits, ..., wsclean-0099-image.fits (and similarly for the psf, residual and dirty). Additionally, images named like wsclean-MFS-image.fits will be outputted, which are the weighted sum over all 100 images.

-Currently, WSClean does not output these images in a normal "imaging cube" like CASA does, i.e., a single fits file with several images in it. This might become an option later (see [Ticket #24](tickets:#24)), but for now one has to combine the output yourself, e.g. with Python.
+WSClean does not output these images in a normal "imaging cube" like CASA does, i.e., a single fits file with several images in it. There is a ticket to do this at a later time (see [Ticket #24](tickets:#24)), but for now I've decided not to implement this (one of the reasons for this is that information about the synthesized beam is not properly stored in a multi-frequency fits file). One has of course the option to combine the output manually, e.g. with a simple Python script.

 When you are interested in only a partial range of channels, the '`-channel-range`' parameter can be used to select that range. For example:

MakingImageCubes modified by André Offringa

André Offringa — Fri, 01 Dec 2017 12:12:54 -0000

--- v6
+++ v7
@@ -1,34 +1,34 @@
 WSClean allows making image cubes, but it works slightly different compared to CASA. The following section describes how it works in WSClean.

-To make image cubes with WSClean, the '-channelsout' parameter is used. This parameter specifies the number of different frequencies for which information will be present in the output.
+To make image cubes with WSClean, the '`-channels-out`' parameter is used. This parameter specifies the number of different frequencies for which information will be present in the output.

-Assume we have a measurement set 'myobservation.ms' with 100 channels. To image each channel seperately, '-channelsout 100' is added to the command line, for example:
+Assume we have a measurement set 'myobservation.ms' with 100 channels. To image each channel seperately, '-channels-out 100' is added to the command line, for example:

     :::bash
-    wsclean -scale 1amin -size 3072 3072 -niter 1000 -threshold 1 -channelsout 100 myobservation.ms
+    wsclean -scale 1amin -size 3072 3072 -niter 1000 -threshold 1 -channels-out 100 myobservation.ms

 This will output 100 images, named wsclean-0000-image.fits, wsclean-0001-image.fits, ..., wsclean-0099-image.fits (and similarly for the psf, residual and dirty). Additionally, images named like wsclean-MFS-image.fits will be outputted, which are the weighted sum over all 100 images.

 Currently, WSClean does not output these images in a normal "imaging cube" like CASA does, i.e., a single fits file with several images in it. This might become an option later (see [Ticket #24](tickets:#24)), but for now one has to combine the output yourself, e.g. with Python.

-When you are interested in only a partial range of channels, the '-channelrange' parameter can be used to select that range. For example:
+When you are interested in only a partial range of channels, the '`-channel-range`' parameter can be used to select that range. For example:

     :::bash
-    wsclean -scale 1amin -size 3072 3072 -niter 1000 -threshold 1 -channelrange 60 70 -channelsout 10 myobservation.ms
+    wsclean -scale 1amin -size 3072 3072 -niter 1000 -threshold 1 -channel-range 60 70 -channels-out 10 myobservation.ms

 This would image channels 60 to 70 and output separate images for each channel.

-The channelsout parameter can be smaller than the available number of input channels. For example, a measurement set with 100 channels can be imaged with "-channelsout 2", which will divide the bandwidth in 2 and output 2 images. Furthermore, you can also specify multiple measurement sets at different frequencies. In such a case, the total bandwidth will be divided into the requested number of channels. For example:
+The channelsout parameter can be smaller than the available number of input channels. For example, a measurement set with 100 channels can be imaged with "`-channels-out 2`", which will divide the bandwidth in 2 and output 2 images. Furthermore, you can also specify multiple measurement sets at different frequencies. In such a case, the total bandwidth will be divided into the requested number of channels. For example:

 Example:

     :::bash
-    wsclean -channelsout 3 -niter 10000 -mgain 0.8 -threshold 0.01 \
+    wsclean -channels-out 3 -niter 10000 -mgain 0.8 -threshold 0.01 \
     band-100-MHz.ms band-110-MHz.ms band-145-MHz.ms band-155-MHz band-190-MHz.ms band-200-MHz

 This will output images at 105 MHz, 150 MHz and 195 MHz.

 Some more notes:

-* The '-channelsout' parameter can be used in combination with '-joinchannels' to improve the deconvolution of MFS imaging in wideband scenarios, or to get better SNR during the deconvolution of spectral imaging. This is explained on the [Wideband deconvolution page](WidebandDeconvolution).
+* The '`-channels-out`' parameter can be used in combination with '`-join-channels`' to improve the deconvolution of MFS imaging in wideband scenarios, or to get better SNR during the deconvolution of spectral imaging. This is explained on the [Wideband deconvolution page](WidebandDeconvolution).
 * WSClean normally weights each output channel separately. This is equivalent to how other imagers do this. However, this is not always desired, especially not with the MWA with its many channels. Therefore, a special weighting mode called 'MFS weighting' has been implemented in WSClean to improve weighting of spectral cubes. This is further explained on the [MFS weighting page](MFSWeighting).

MakingImageCubes modified by André Offringa

André Offringa — Sun, 23 Aug 2015 09:38:37 -0000

--- v5
+++ v6
@@ -18,7 +18,17 @@

 This would image channels 60 to 70 and output separate images for each channel.

+The channelsout parameter can be smaller than the available number of input channels. For example, a measurement set with 100 channels can be imaged with "-channelsout 2", which will divide the bandwidth in 2 and output 2 images. Furthermore, you can also specify multiple measurement sets at different frequencies. In such a case, the total bandwidth will be divided into the requested number of channels. For example:
+
+Example:
+
+    :::bash
+    wsclean -channelsout 3 -niter 10000 -mgain 0.8 -threshold 0.01 \
+    band-100-MHz.ms band-110-MHz.ms band-145-MHz.ms band-155-MHz band-190-MHz.ms band-200-MHz
+
+This will output images at 105 MHz, 150 MHz and 195 MHz.
+
 Some more notes:

-* The '-channelsout' parameter can be used in combination with '-joinchannels' to improve the deconvolution of MFS imaging in wideband scenarios, or to get better SNR during the deconvolution of spectral imaging. This is explained on the [Wideband imaging page](WidebandImaging).
+* The '-channelsout' parameter can be used in combination with '-joinchannels' to improve the deconvolution of MFS imaging in wideband scenarios, or to get better SNR during the deconvolution of spectral imaging. This is explained on the [Wideband deconvolution page](WidebandDeconvolution).
 * WSClean normally weights each output channel separately. This is equivalent to how other imagers do this. However, this is not always desired, especially not with the MWA with its many channels. Therefore, a special weighting mode called 'MFS weighting' has been implemented in WSClean to improve weighting of spectral cubes. This is further explained on the [MFS weighting page](MFSWeighting).

MakingImageCubes modified by André Offringa

André Offringa — Sun, 23 Aug 2015 09:33:30 -0000

--- v4
+++ v5
@@ -2,7 +2,7 @@

 To make image cubes with WSClean, the '-channelsout' parameter is used. This parameter specifies the number of different frequencies for which information will be present in the output.

-Assume we have a measurement set 'myobservation.ms' with 100 channels. To imaging each channel seperately, '-channelsout 100' is added to the command line, for example:
+Assume we have a measurement set 'myobservation.ms' with 100 channels. To image each channel seperately, '-channelsout 100' is added to the command line, for example:

     :::bash
     wsclean -scale 1amin -size 3072 3072 -niter 1000 -threshold 1 -channelsout 100 myobservation.ms

MakingImageCubes modified by André Offringa

André Offringa — Mon, 30 Mar 2015 16:35:48 -0000

--- v3
+++ v4
@@ -14,7 +14,7 @@
 When you are interested in only a partial range of channels, the '-channelrange' parameter can be used to select that range. For example:

     :::bash
-    wsclean -scale 0.01 -size 3072 3072 -niter 1000 -threshold 1 -channelrange 60 70 -channelsout 10 myobservation.ms
+    wsclean -scale 1amin -size 3072 3072 -niter 1000 -threshold 1 -channelrange 60 70 -channelsout 10 myobservation.ms

 This would image channels 60 to 70 and output separate images for each channel.

MakingImageCubes modified by André Offringa

André Offringa — Mon, 30 Mar 2015 16:34:54 -0000

--- v2
+++ v3
@@ -5,7 +5,7 @@
 Assume we have a measurement set 'myobservation.ms' with 100 channels. To imaging each channel seperately, '-channelsout 100' is added to the command line, for example:

     :::bash
-    wsclean -scale 0.01 -size 3072 3072 -niter 1000 -threshold 1 -channelsout 100 myobservation.ms
+    wsclean -scale 1amin -size 3072 3072 -niter 1000 -threshold 1 -channelsout 100 myobservation.ms

 This will output 100 images, named wsclean-0000-image.fits, wsclean-0001-image.fits, ..., wsclean-0099-image.fits (and similarly for the psf, residual and dirty). Additionally, images named like wsclean-MFS-image.fits will be outputted, which are the weighted sum over all 100 images.

MakingImageCubes modified by André Offringa

André Offringa — Sun, 16 Nov 2014 10:56:45 -0000

--- v1
+++ v2
@@ -19,5 +19,6 @@
 This would image channels 60 to 70 and output separate images for each channel.

 Some more notes:
+
 * The '-channelsout' parameter can be used in combination with '-joinchannels' to improve the deconvolution of MFS imaging in wideband scenarios, or to get better SNR during the deconvolution of spectral imaging. This is explained on the [Wideband imaging page](WidebandImaging).
 * WSClean normally weights each output channel separately. This is equivalent to how other imagers do this. However, this is not always desired, especially not with the MWA with its many channels. Therefore, a special weighting mode called 'MFS weighting' has been implemented in WSClean to improve weighting of spectral cubes. This is further explained on the [MFS weighting page](MFSWeighting).

MakingImageCubes modified by André Offringa

André Offringa — Sun, 16 Nov 2014 10:56:13 -0000

WSClean allows making image cubes, but it works slightly different compared to CASA. The following section describes how it works in WSClean.

To make image cubes with WSClean, the '-channelsout' parameter is used. This parameter specifies the number of different frequencies for which information will be present in the output.

Assume we have a measurement set 'myobservation.ms' with 100 channels. To imaging each channel seperately, '-channelsout 100' is added to the command line, for example:

wsclean -scale 0.01 -size 3072 3072 -niter 1000 -threshold 1 -channelsout 100 myobservation.ms

This will output 100 images, named wsclean-0000-image.fits, wsclean-0001-image.fits, ..., wsclean-0099-image.fits (and similarly for the psf, residual and dirty). Additionally, images named like wsclean-MFS-image.fits will be outputted, which are the weighted sum over all 100 images.

Currently, WSClean does not output these images in a normal "imaging cube" like CASA does, i.e., a single fits file with several images in it. This might become an option later (see Ticket #24), but for now one has to combine the output yourself, e.g. with Python.

When you are interested in only a partial range of channels, the '-channelrange' parameter can be used to select that range. For example:

wsclean -scale 0.01 -size 3072 3072 -niter 1000 -threshold 1 -channelrange 60 70 -channelsout 10 myobservation.ms

This would image channels 60 to 70 and output separate images for each channel.

Some more notes:
The '-channelsout' parameter can be used in combination with '-joinchannels' to improve the deconvolution of MFS imaging in wideband scenarios, or to get better SNR during the deconvolution of spectral imaging. This is explained on the Wideband imaging page.
WSClean normally weights each output channel separately. This is equivalent to how other imagers do this. However, this is not always desired, especially not with the MWA with its many channels. Therefore, a special weighting mode called 'MFS weighting' has been implemented in WSClean to improve weighting of spectral cubes. This is further explained on the MFS weighting page.