Using VIS

VIS should always be running on XBONES, with the display appearing on PERICLES in the Control Room.

To start VIS, login to XBONES and enter:
$ vis.

You may have to set your display to your local environment with:
$set display/create/node=pericles/transport=tcpip

Once VIS has loaded, you will be invited to state what data to display and to select which baselines be plotted. The data options offered are listed. You can change the visibility types displayed at any time. Just type one of the commands.

Table 8.2: VIS quantities.

Symbol	Quantity
a	Amplitude
b	Effective baseline $\sqrt{u^2~+~v^2}$
c	Closure phase (must use closure to define)
d	Delay
e	Elevation
f	Observing frequency
g	Square of amplitude
h	Hour Angle
i	Imaginary part of the visibility
k	Parallactic angle
l	LO (Local Oscillator) 1-way phase correction (also use 0)
n	Integration cycles
p	Phase
q	Quotient of Vector averaged and scalar averaged visibilities, useful to check tied array phase coherence
r	Real part of the visibility
s	Sum, actually the vector average of the visibilities
t	Time
u	Baseline vector $u$
v	Baseline vector $v$
w	Baseline vector $w$
x	Right Ascension
y	Declination
z	Azimuth
0	LO phase correction scale
1	User definable monitor point
2	User definable monitor point
3	User definable monitor point

You can change the type of visibility displayed at any time. To display a set of parameters, type in the letter of the x-axis followed by letters for the y-axes (with no separating spaces). Up to three plots can be displayed at once, but they will all share a common x-axis. For example:

	VIS$>$ tdpa		To plots amplitude, delay and phase versus time.
	VIS$>$ tap		Plots just amplitude and phase against time.

Many observers are interested in t & a although it can be very interesting to look at the $uv$ tracks of the array by using VIS$>$uv. Note: VIS can hold a total of 13 hours of visibility data.

You can specify the y-axis scaling using:

	VIS$>$ scale		To auto-scale all plots.
	Or for example:
	VIS$>$ scale a 0 10		To scale the amplitude plot ordinate from 0 to 10Jy.

To change the x-axis scaling use the history command. For example:

VIS$>$ hist 1h

To display the last hour of data.

Figure 8.10: Example of a VIS uv display.