Inconsistencies between UVPLT and TVFLG?

Here's a question from Anonymous:

I am re-reducing 1667 MHz OH spectral line data from project AC319 (JUN-92, polarizations RR, LL, RL, LR). I chose one spectral channel from one day, and I plotted the visibility amplitudes with both TVFLG and UVPLT. The data are split, and they are for the program source W22.

I plotted the visibility amplitudes in UVPLT (stokes 'rr'), and I don't see any amplitudes over 20 Jy for baseline lengths 4 - 9 kilolambda. However, when I plot the same data in TVFLG (stokes 'rr', sorted by length), I see a number of amplitudes higher than 20 Jy in the same baseline range.

Why would the higher amplitudes be displayed by TVFLG but not by UVPLT? In both cases, I chose flagver =-1, so no flagging should have been applied when I ran either task.

I'm not sure of the exact answer to your question, but there are lots of ways for TVFLG and UVPLT to give slightly different pictures of your data:

--Is XINC set in UVPLT?
--Are you sure your looking at the same channel in each case, and not averaging channels in either case?
--TVFLG may be secretly time averaging your visibilities. To make sure that it's not time averaging, find out what your integration time is and input this as DPARM(6). Then, once the data are actually loaded, look at the AVG parameter stated in the bottom left of the tv screen. If it is set to a number greater than 1, than time averaging is occurring. To change this averaging time, click on 'enter smooth time'.

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Getting rid of distracting black lines in TVFLG/SPFLG

Have you ever loaded your data into TVFLG or SPFLG and seen what looks like lots of blank times (manifested as horizontal black lines cutting through your data)?

This is because TVFLG/SPFLG is trying to load your data with a time bin that is not a multiple of your integration time. So---the solution is to set DPARM(6)! Set DPARM(6) to your integration time in seconds; e.g., for GMRT data:

DPARM(6) = 16.7

(or, if you have time averaged your data, set it equal to your averaging time).

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Missing Scans!

I'm reducing some EVLA-VLA data, and I discovered that one of the calibrator scans was missing in the data. It was listed in the "scan list" on the archive and the observe files were (to the best of our knowledge) correct. After emailing the analysts, we figured out that the scan was flagged by the online flagger. You can read in the data without applying these online flags using CPARM(3) = 16.

I'm still trying to figure out why it was flagged, and I'm assuming that this information is stored in the "OF Table" extension. However, I haven't been able to find any information on that table using google (googling "aips 'OF table'" doesn't really work because you get a lot of pages with properties of tables, not info about the OF table).

I'll post what I learn about this (if anything), but it's something to keep in mind if you find yourself missing scans..

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How does DBCON deal with flagging?

Does anybody out there understand how DBCON flags your data? The help file is being less than transparent. DBCON seems to copy over all the FG tables from the first image you give it to the DBCON'd file, but does not appear to copy FG tables from the second image.

There is this note in the help file:
"Also, any CL, FG, TY, WX, IM, MC, PC, AT, CT, OB, or GC tables with version=1 will have their source numbers translated and appended to the end of the corresponding table (if any) from the first file."
So, let's say I have 13 flag tables for Image1 and 6 flag tables for Image2 (which happens a lot with the new crazy FG table creation scheme). Does this mean FG #1 for Image2 gets appended to FG tables 1-13 from Image1? And then in the futere, I will be apply a combination of FG#1 to Image1 and FG #13 to Image2? That's kinda dumb...

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Two More Ways to Identify Bad Data

Crystal also said a good way to identify RFI is to look at Stokes V, either in TVFLG or UVPLT or whatever. RFI is usually polarized and will pop out as unusually high baselines/channels/times.

Stokes V will usually mimic your amplitude structure (as a function of baseline length). So, for example, if your source has high amplitudes at short baselines, Stokes V should also be a bit higher on these short baselines (so don't get confused and flag them).

And another way to find that bad data-- Data weights. Plot your data in UVPLT with BPARM = 0 13. The weights for all the data should cluster-- if there are any points that are anomalously low or high, flag them! Crystal says she likes to use WIPER. Obviously, be more concerned about data with really high weights that really low weights-- because this data will affect your overall data set more, as it is up-weighted!

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Don't Clip Your Data!

I'm at the GBT, and just had a nice long chat with Crystal Brogan (who was very helpful when she reeally didn't need to be). I'm gonna list a few tips she suggests.

Here's one: DON'T CLIP!! She said that if you clip your data based on amplitude (or phase), what you're really doing is masking the lower-level bad data. A baseline is probably all bad if it has quite a few high points, and you don't want to just flag the really high stuff, you want to flag it all. If you clip the high stuff, it will be very hard to ever identify that whole baseline as bad. You'll essentially be 'losing' bad data. I know CLIPing is sometimes tempting, especially at the GMRT, but I can see that it's an especially bad idea in this case.

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Bins in UVPLT

You know what is a great easy way to visualize your data that I often forget about? Bin your data in UVPLT! For example, if you are making a UV distance vs. Amplitude plot, then you can actually see the amplitude structure instead of just seeing tons of points ranging all the way down to an amplitude of zero.

All you have to do is set BPARM(8) = 50 or the number of bins you want.

I think it also plots up faster this way then plotting lots of individual points!
Of course, if what you care about is a handful of really pathelogical points, than this is not the right strategy. But if you are, say, trying to identify a bad baseline or something, this works great!

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Flagging After A&P Self Calibration?

I've been wondering lately-- when you run an Amplitude & Phase Self-Cal run, often times this can make certain parts of your data look anomalously high or low. Usually it's pretty mild, but a couple of times, it has been rather dramatic. A bit distressing, as I don't really understand why CALIB chose to make my amplitudes worse...

But anyway, does anyone out there have opinions on whether you should flag your data again after an A&P self cal? If you do flag, do you then copy the flag table over to the un-A&P-self-calibrated data set, and the re-self-calibrate using this new flag table? And iterate so on till no more "bad" data pops up on the A&P self cal?

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Where did R go?

Ok, this is kind of a strange thing. I'm working with Pband data. I've gone through initial flagging, and then I run CALIB. But for some reason it's not finding my R data... so I get 1/2 good solutions and 1/2 failed solutions (because it finds the L just fine). But I look at the data (and when I flagged it too) and it's *there*. Has anyone encountered this? What's going on and how to I fix it? I'm using pretty standard inputs...

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WBR Step 5L: Flag Your Calibrators

Ok, 'L' stands for Line data. Most of the steps for reducing line data can also be found in Appendix B of the AIPS cookbook. What we have to do first is flag the Channel 0 data for our calibrators.


First, you should know that flagging is really a matter of personal taste. This is the way I like to do it, but you might find something that you like a whole lot more.

Secondly, don't be surprised when flagging is by far the most time consuming aspect of interferometric data reduction. Especially if you're screwing around with data from the VLA as it is transitioning to the EVLA.

Thirdly, at least at this stage, only flag on amplitude. After some calibration, you might consider flagging on phase, but not yet.

A good place to start flagging is QUACK. QUACK flags the beginning of each scan of data, because often times the first little bit of time on an object is bad. QUACK from the 31Dec05 release of AIPS was really quite transparent, with parameters looking like this:

AIPS 1: QUACK     Flags specified portion of scans of UV data
AIPS 1: Adverbs     Values                 Comments
AIPS 1: ----------------------------------------------------------------
AIPS 1: INNAME     'AC825_FQ1'             Input UV file name (name)
AIPS 1: INCLASS    'CH 0'                  Input UV file name (class)
AIPS 1: INSEQ         1                    Input UV file name (seq. #)
AIPS 1: INDISK        1                    Input UV file disk unit #
AIPS 1: SOURCES    *all ' '                Sources selected/deselected
AIPS 1: SUBARRAY      0                    Subarray number 0=>all.
AIPS 1: SELBAND      -1                    Bandwidth to flag (kHz)
AIPS 1: SELFREQ      -1                    Frequency to flag (MHz)
AIPS 1: FREQID        1                    Freq. ID to flag. -1=>all.
AIPS 1:                                    0=> first Freq. ID.
AIPS 1: TIMERANG   *all 0                  Time: start day,hr,min,sec
AIPS 1:                                          stop day,hr,min,sec.
AIPS 1: ANTENNAS   *all 0                  Antennas to flag
AIPS 1: FLAGVER       0                    Flag table version number
AIPS 1: OPCODE     'ENDB'                  'END ', 'BEG ', 'ENDB'
AIPS 1:                                    'TAIL';   ' ' => 'BEG '
AIPS 1: REASON     *all ' '                Reason (24 char.)
AIPS 1: APARM         0            .33     (1) => Cutting time (min)
AIPS 1:            *rest 0                 from end (ENDG) 0 => 2
AIPS 1:                                    (2) => Cutting time (min)
AIPS 1:                                    from beg/end (BEGB/ENDB)
AIPS 1:                                    0 => 0.1
AIPS 1:                                    (3) Back start of flagging
AIPS 1:                                     <0 => no padding (0 seconds)
AIPS 1:                                      0 => 5 seconds [default]
AIPS 1:                                     >0 => APARM(3) seconds

In this case, I'm flagging the last third of a minute in each scan. If you wanted to flag the first part of a scan, you would set
OPCODE = 'BEG'. The Dec07 version of QUACK is really different and I don't understand it yet. Maybe someone can write in with pointers about it?

Good. Next, I like to look at my data in TVFLG and give it a quick flag. Here are some important parameters to consider before your run TVFLG.
SOURCES-- only look at one calibrator at a time in TVFLG. Otherwise your scale will be all messed up and you'll be confused.
TIMERANG-- You really really want all of your data to be able to fit with a smooth time of 10 seconds. What will happen is that if there is too much time spent on your source, AIPS will force you to average your data for multiples of 10s, and this is bad. Because you will flag your data, and think you got rid of the really bright points, but then you will look at all the visibilities in UVPLT and still see lots of bright points. You will be in for far fewer nasty surprises if you make sure smooth time is 10s (In the TVFLG window, it should say AVG 1). Therefore, if you're getting AVG > 1, you should probably break your data up and view it several times in TVFLG with different timeranges. You probably won't know if you need to set a timerange until you load up TVFLG once, and see how much data there is.
DOCAL = 2-- apply weights to your data before you view them in TVFLG.

AIPS 1: TVFLG:  Task to edit UV data using the TV display and cursor
AIPS 1: Adverbs     Values                 Comments
AIPS 1: ----------------------------------------------------------------
AIPS 1: USERID        0                    User number.
AIPS 1: INNAME     'AC825_FQ1'             UV data (name).
AIPS 1: INCLASS    'CH 0'                  UV data (class).
AIPS 1: INSEQ         1                    UV data (seq. #).  0 => high
AIPS 1: INDISK        1                    Disk unit #.       0 => any
AIPS 1: DOCAT         0                    Catalog work file ?
AIPS 1: IN2SEQ        1                    Sequence number of work file
AIPS 1: IN2DISK       1                    Disk number of work file
AIPS 1: DOHIST       -1                    Record flags in history file
AIPS 1: SOURCES    '1331+305'              Source list
AIPS 1:            *rest ' '
AIPS 1: CALCODE    ' '                     Calibrator code '    '=>all
AIPS 1: TIMERANG   *all 0                  Time range to include
AIPS 1: STOKES     ' '                     Stokes type to display
AIPS 1: SELBAND      -1                    Bandwidth to select (kHz)
AIPS 1: SELFREQ      -1                    Frequency to select (MHz)
AIPS 1: FREQID        0                    Freq. ID to select.
AIPS 1: BIF           0                    Lowest IF number 0=1
AIPS 1: EIF           0                    Highest IF number
AIPS 1: BCHAN         0                    Lowest channel number 0=>1
AIPS 1: ECHAN         0                    Highest channel number
AIPS 1: ANTENNAS   *all 0                  Antennas to include
AIPS 1: BASELINE   *all 0                  Baselines with ANTENNAS
AIPS 1: UVRANGE       0           0        UV range in kilolambda
AIPS 1: SUBARRAY      0                    Subarray, 0 => all, but the
AIPS 1:                                    task is more efficient doing
AIPS 1:                                    one at a time
AIPS 1:                                    Cal. info for input:
AIPS 1: DOCALIB       2                    If >0 calibrate data
AIPS 1:                                    = 2 calibrate weights
AIPS 1: GAINUSE       1                    CAL (CL or SN) table to apply
AIPS 1: DOPOL        -1                    If >0 correct polarization.
AIPS 1: BLVER        -1                    BL table to apply.
AIPS 1: FLAGVER       1                    Flag table version 0 => high
AIPS 1:                                       < 0 no flagging on input
AIPS 1:                                       Used w single-source too
AIPS 1: DOBAND       -1                    If >0 apply bandpass cal.
AIPS 1:                                    Method used depends on value
AIPS 1:                                    of DOBAND (see HELP file).
AIPS 1: BPVER         0                    Bandpass table version
AIPS 1: SMOOTH     *all 0                  Smoothing function. See
AIPS 1:                                    HELP SMOOTH for details.
AIPS 1: DPARM         0           0        Control info:
AIPS 1:               0           0        (1) 0=amp, 1=phase, 2=rms,
AIPS 1:              10          10            3=rms/mean for initial
AIPS 1:            *rest 0                     display, can choose any
AIPS 1:                                        interactively later
AIPS 1:                                    (2) > 0 include autocorr data
AIPS 1:                                    (3) >0 = baseline as ant pair
AIPS 1:                                        for B as x-axis only
AIPS 1:                                    (4) >0 => divide by source
AIPS 1:                                        IPOL flux
AIPS 1:                                    (5) Expand time ranges by
AIPS 1:                                        DPARM(5) in sec
AIPS 1:                                    (6) y-axis interval: give the
AIPS 1:                                        sample time in seconds.
AIPS 1:                                        default = 10 seconds.
AIPS 1:                                    (7) initial IF displayed, 0
AIPS 1:                                        => BIF, can choose BIF -
AIPS 1:                                        EIF interactively
AIPS 1:                                    (8) initial channel displayed
AIPS 1:                                        0 => BCHAN, can choose
AIPS 1:                                        BCHAN - ECHAN later
AIPS 1:                                        interactively
AIPS 1:                                    (9,10) pixrange for initial
AIPS 1:                                        TV load - can reset later
AIPS 1:                                        interactively
AIPS 1: BADDISK    *all 0                  Disks to avoid for scratch
AIPS 1:                                    and for master grid file.

Make sure that you look at all your channels, polarizations, and IFs. I like the 'clip interactively' command a lot for getting rid of high or low points.

I recently (finally!) figured out how to invert the scale in TVFLG, so that low points appear bright. Use the 'tvtransf' option, type an 'a' to get an option to change the contrast/brightness of the image. A little square will pop up. Type 'c' now to invert the image, and then move your mouse around with the button held down to get an image stretch you like. Tah Dah!

One useful note: You have to set the Stokes Flag in terms of 0's and 1's, and this is what the binary code means:
1000-- flag only right polarization
0100--flag only left polarization
1111--flag both polarizations

NOTE: TVFLG can take a long time to load if you have lots of channels or data. It's usually pretty fast for the calibrators, because you don't usually spend much time on them. But while TVFLG is loading up your target data (no, we're not there yet), you might want to go eat lunch. Depending on the data set.

Finally, double check everything in UVPLT. Beware, UVPLT likes to plot data in terms of Stokes I, which is quite confusing. Choose to plot STOKES = 'RR' or 'LL' for more clarity. BPARM is the important set of parameters which mostly determine what you're plotting. BPARM = 0 is a good place to start, as this plots amplitude against the length of your baselines.

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WBR Step 5C. Flag Your Calibrators

Ok, 'C' stands for continuum. There are slightly different calibration steps for deep continuum data; I'm going to follow the tips for L-Band data reduction given at this VLA website. That means we won't be using the CH 0 data, we'll be making our own Channel 0 after we bandpass-calibrate the line data. But I'm getting ahead of myself. What we have to do first is flag our calibrators. I like to only flag the calibrators very lightly, then calibrate them, and then flag more heavily on the calibrated data.


First, you should know that flagging is really a matter of personal taste. This is the way I like to do it, but you might find something that you like a whole lot more.

Secondly, don't be surprised when flagging is by far the most time consuming aspect of interferometric data reduction. Especially if you're screwing around with data from the VLA as it is transitioning to the EVLA.

Thirdly, at least at this stage, only flag on amplitude. After some calibration, you might consider flagging on phase, but not yet.

Fourthly, before you calibrate, I recommend you only flag on dramatically bad looking amplitudes. Don't get too selective yet.

So, as I mentioned above, let's run all of the below commands on the line data. This is more work for you, as you have to look at each channel, but it seems to be the more meticulous way of doing it. If you prefer, I guess you could flag on your CH 0 data, then just copy over the flag (FG) table (using TACOP) to the LINE data set. That might be faster. But you still should probable do a brief run through each channel to make sure there's nothing really glaring that you missed, when you averaged all the channels together.

A good place to start flagging is QUACK. QUACK flags the beginning of each scan of data, because often times the first little bit of time on an object is bad. QUACK from the 31Dec05 release of AIPS was really quite transparent, with parameters looking like this:

AIPS 1: QUACK     Flags specified portion of scans of UV data
AIPS 1: Adverbs     Values                 Comments
AIPS 1: ----------------------------------------------------------------
AIPS 1: INNAME     'AC825_FQ1'             Input UV file name (name)
AIPS 1: INCLASS    'LINE'                  Input UV file name (class)
AIPS 1: INSEQ         1                    Input UV file name (seq. #)
AIPS 1: INDISK        1                    Input UV file disk unit #
AIPS 1: SOURCES    *all ' '                Sources selected/deselected
AIPS 1: SUBARRAY      0                    Subarray number 0=>all.
AIPS 1: SELBAND      -1                    Bandwidth to flag (kHz)
AIPS 1: SELFREQ      -1                    Frequency to flag (MHz)
AIPS 1: FREQID        1                    Freq. ID to flag. -1=>all.
AIPS 1:                                    0=> first Freq. ID.
AIPS 1: TIMERANG   *all 0                  Time: start day,hr,min,sec
AIPS 1:                                          stop day,hr,min,sec.
AIPS 1: ANTENNAS   *all 0                  Antennas to flag
AIPS 1: FLAGVER       0                    Flag table version number
AIPS 1: OPCODE     'ENDB'                  'END ', 'BEG ', 'ENDB'
AIPS 1:                                    'TAIL';   ' ' => 'BEG '
AIPS 1: REASON     *all ' '                Reason (24 char.)
AIPS 1: APARM         0            .33     (1) => Cutting time (min)
AIPS 1:            *rest 0                 from end (ENDG) 0 => 2
AIPS 1:                                    (2) => Cutting time (min)
AIPS 1:                                    from beg/end (BEGB/ENDB)
AIPS 1:                                    0 => 0.1
AIPS 1:                                    (3) Back start of flagging
AIPS 1:                                     <0 => no padding (0 seconds)
AIPS 1:                                      0 => 5 seconds [default]
AIPS 1:                                     >0 => APARM(3) seconds

In this case, I'm flagging the last third of a minute in each scan. If you wanted to flag the first part of a scan, you would set
OPCODE = 'BEG'. The Dec07 version of QUACK is really different and I don't understand it yet. Maybe someone can write in with pointers about it?

Good. Next, I like to look at my data in TVFLG and give it a quick flag. Here are some important parameters to consider before your run TVFLG.
SOURCES-- only look at one calibrator at a time in TVFLG. Otherwise your scale will be all messed up and you'll be confused.
TIMERANG-- You really really want all of your data to be able to fit with a smooth time of 10 seconds. What will happen is that if there is too much time spent on your source, AIPS will force you to average your data for multiples of 10s, and this is bad. Because you will flag your data, and think you got rid of the really bright points, but then you will look at all the visibilities in UVPLT and still see lots of bright points. You will be in for far fewer nasty surprises if you make sure smooth time is 10s (In the TVFLG window, it should say AVG 1). Therefore, if you're getting AVG > 1, you should probably break your data up and view it several times in TVFLG with different timeranges. You probably won't know if you need to set a timerange until you load up TVFLG once, and see how much data there is.
DOCAL = 2-- apply weights to your data before you view them in TVFLG.

AIPS 1: TVFLG:  Task to edit UV data using the TV display and cursor
AIPS 1: Adverbs     Values                 Comments
AIPS 1: ----------------------------------------------------------------
AIPS 1: USERID        0                    User number.
AIPS 1: INNAME     'AC825_FQ1'             UV data (name).
AIPS 1: INCLASS    'CH 0'                  UV data (class).
AIPS 1: INSEQ         1                    UV data (seq. #).  0 => high
AIPS 1: INDISK        1                    Disk unit #.       0 => any
AIPS 1: DOCAT         0                    Catalog work file ?
AIPS 1: IN2SEQ        1                    Sequence number of work file
AIPS 1: IN2DISK       1                    Disk number of work file
AIPS 1: DOHIST       -1                    Record flags in history file
AIPS 1: SOURCES    '1331+305'              Source list
AIPS 1:            *rest ' '
AIPS 1: CALCODE    ' '                     Calibrator code '    '=>all
AIPS 1: TIMERANG   *all 0                  Time range to include
AIPS 1: STOKES     ' '                     Stokes type to display
AIPS 1: SELBAND      -1                    Bandwidth to select (kHz)
AIPS 1: SELFREQ      -1                    Frequency to select (MHz)
AIPS 1: FREQID        0                    Freq. ID to select.
AIPS 1: BIF           0                    Lowest IF number 0=1
AIPS 1: EIF           0                    Highest IF number
AIPS 1: BCHAN         0                    Lowest channel number 0=>1
AIPS 1: ECHAN         0                    Highest channel number
AIPS 1: ANTENNAS   *all 0                  Antennas to include
AIPS 1: BASELINE   *all 0                  Baselines with ANTENNAS
AIPS 1: UVRANGE       0           0        UV range in kilolambda
AIPS 1: SUBARRAY      0                    Subarray, 0 => all, but the
AIPS 1:                                    task is more efficient doing
AIPS 1:                                    one at a time
AIPS 1:                                    Cal. info for input:
AIPS 1: DOCALIB       2                    If >0 calibrate data
AIPS 1:                                    = 2 calibrate weights
AIPS 1: GAINUSE       1                    CAL (CL or SN) table to apply
AIPS 1: DOPOL        -1                    If >0 correct polarization.
AIPS 1: BLVER        -1                    BL table to apply.
AIPS 1: FLAGVER       1                    Flag table version 0 => high
AIPS 1:                                       < 0 no flagging on input
AIPS 1:                                       Used w single-source too
AIPS 1: DOBAND       -1                    If >0 apply bandpass cal.
AIPS 1:                                    Method used depends on value
AIPS 1:                                    of DOBAND (see HELP file).
AIPS 1: BPVER         0                    Bandpass table version
AIPS 1: SMOOTH     *all 0                  Smoothing function. See
AIPS 1:                                    HELP SMOOTH for details.
AIPS 1: DPARM         0           0        Control info:
AIPS 1:               0           0        (1) 0=amp, 1=phase, 2=rms,
AIPS 1:              10          10            3=rms/mean for initial
AIPS 1:            *rest 0                     display, can choose any
AIPS 1:                                        interactively later
AIPS 1:                                    (2) > 0 include autocorr data
AIPS 1:                                    (3) >0 = baseline as ant pair
AIPS 1:                                        for B as x-axis only
AIPS 1:                                    (4) >0 => divide by source
AIPS 1:                                        IPOL flux
AIPS 1:                                    (5) Expand time ranges by
AIPS 1:                                        DPARM(5) in sec
AIPS 1:                                    (6) y-axis interval: give the
AIPS 1:                                        sample time in seconds.
AIPS 1:                                        default = 10 seconds.
AIPS 1:                                    (7) initial IF displayed, 0
AIPS 1:                                        => BIF, can choose BIF -
AIPS 1:                                        EIF interactively
AIPS 1:                                    (8) initial channel displayed
AIPS 1:                                        0 => BCHAN, can choose
AIPS 1:                                        BCHAN - ECHAN later
AIPS 1:                                        interactively
AIPS 1:                                    (9,10) pixrange for initial
AIPS 1:                                        TV load - can reset later
AIPS 1:                                        interactively
AIPS 1: BADDISK    *all 0                  Disks to avoid for scratch
AIPS 1:                                    and for master grid file.

Make sure that you look at all your channels, polarizations, and IFs. I like the 'clip interactively' command a lot for getting rid of high or low points.

I recently (finally!) figured out how to invert the scale in TVFLG, so that low points appear bright. Use the 'tvtransf' option, type an 'a' to get an option to change the contrast/brightness of the image. A little square will pop up. Type 'c' now to invert the image, and then move your mouse around with the button held down to get an image stretch you like. Tah Dah!

One useful note: You have to set the Stokes Flag in terms of 0's and 1's, and this is what the binary code means:
1000-- flag only right polarization
0100--flag only left polarization
1111--flag both polarizations

NOTE: TVFLG can take a long time to load if you have lots of channels or data. It's usually pretty fast for the calibrators, because you don't usually spend much time on them. But while TVFLG is loading up your target data (no, we're not there yet), you might want to go eat lunch. Depending on the data set.

Finally, double check everything in UVPLT. Beware, UVPLT likes to plot data in terms of Stokes I, which is quite confusing. Choose to plot STOKES = 'RR' or 'LL' for more clarity. BPARM is the important set of parameters which mostly determine what you're plotting. BPARM = 0 is a good place to start, as this plots amplitude against the length of your baselines.

Read more!

tvflg outputs

Quicky: How do I keep TVFLG from making those stupid .TVFLG. files whenever I use it?

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