AMPRATIO( ) = _REAL (Read)
If number of beam positions given by BEAMS is more
than one, this specifies the ratio of the amplitude of the secondary beams to the primary. Thus you
should supply one fewer value than the number of beams. If you give fewer than that the
last ratio is copied to the missing values. The ratios would normally be negative, usually
AMPRATIO is ignored when there is only one beam feature to fit.
BEAMS = _INTEGER
The number of beam positions to fit. This will normally be 1, unless a chopped
observation is supplied, when there may be two or three beam positions. This parameter is
"Catalogue" modes, where the number comes from the number
of beam positions read from the files; and for "Interface" mode when the beam positions
POS, POS2, etc. are supplied in full on the command line without BEAMS. In all modes
there is a maximum of five positions, which for
"Catalogue" modes will be
the first five.
CIRCULAR = _LOGICAL (Read)
TRUE only circular beams will
COIN = FILENAME (Read)
Name of a text file containing the initial
guesses at the co-ordinates of beams to be fitted. It is only accessed if Parameter MODE is
given the value
. Each line should contain the formatted axis values
for a single
position, in the current Frame
of the NDF. Axis values can be separated by spaces, tabs or
commas. The file may contain comment lines with the first character
TRUE, a detailed description of the co-ordinate Frame in which the
beam positions will be reported is displayed before the positions themselves.
DEVICE = DEVICE (Read)
The graphics device which is to be used to give the
initial guesses at the beam positions. Only accessed if Parameter MODE is given the value
[Current graphics device
FITAREA() = _INTEGER (Read)
Size in pixels of
the fitting area to be used. This should fully encompass the beam and also include some
background signal. If only a single value is given, then it will be duplicated to all dimensions
so that a square region is fitted. Each value must be at least 9. A null value requests that
the full data array is used.
FIXAMP = _DOUBLE (Read)
This specifies the fixed
amplitude of the first beam. Secondary sources arising from chopped data use FIXAMP
multiplied by the AMPRATIO. A null value indicates that the amplitude should be fitted.
FIXBACK = _DOUBLE (Read)
If a non-null value is supplied then the model fit will use that
value as the constant background level otherwise the background is a free parameter of the
FIXFWHM = LITERAL (Read)
If this is set
TRUE then the model fit will use the
full-width half-maximum values for the beams supplied through Parameter FWHM.
demands that the FWHM values are free parameters of the fit.
FIXPOS = _LOGICAL
TRUE, the supplied position of each beam is used and the centre co-ordinates of the
beam features are not fit.
FALSE causes the initial estimate of the location of each beam to
come from the source selected by Parameter MODE, and all these locations are part of the
fitting process (however note the exception when FIXSEP=
TRUE. It is advisable not to use
this option in the inaccurate
FIXSEP = _LOGICAL (Read)
TRUE, the separations of secondary beams from the primary beam are fixed, and this takes
precedence over Parameter FIXPOS. If
FALSE, the beam separations are free to be fitted
(although it is actually the centres being fit). It is advisable not to use this option in the
FWHM = LITERAL (Read)
The initial full-width
half-maximum (FWHM) values for each beam. These become fixed values if FIXFWHM is set
A number of options are available.
A single value gives the same circular FWHM for all beams.
When Parameter CIRCULAR is
TRUE, supply a list of values one for each of the number of beams.
These should be supplied in the same order as the corresponding beam positions.
A pair of values sets the major- and minor-axis values for all beams, provided Parameter CIRCULAR
Major- and minor-axis pairs, whose order should match that of the corresponding beams. Again
CIRCULAR should be
Multiple values are separated by commas. An error is issued should none of these options be
If the current co-ordinate Frame of the NDF is a SKY Frame (e.g. right ascension and declination), then
the value should be supplied as an increment of celestial latitude (e.g. declination). Thus,
"20:0" would mean 20 arcminutes, and
"1:0:0" would mean 1 degree. If the current
co-ordinate Frame is not a SKY Frame, then the widths should be specified as an increment along Axis
1 of the current co-ordinate Frame. Thus, if the Current Frame is PIXEL, the value should be given
simply as a number of pixels.
Null requests that BEAMFIT itself estimates the initial FWHM values.
GAUSS = _LOGICAL
TRUE, the shape exponent is fixed to be 2; in other words the beams are modelled as
two-dimensional normal distributions. If
FALSE, the shape exponent is a free parameter in
INCAT = FILENAME (Read)
A catalogue containing a positions list
giving the initial guesses at the beam positions, such as produced by applications CURSOR,
LISTMAKE, etc. It is only accessed if Parameter MODE is given the value
LOGFILE = FILENAME (Read)
Name of the text file to log the results. If null, there
will be no logging. Note this is intended for the human reader and is not intended for
passing to other applications.
MARK = LITERAL (Read)
Only accessed if Parameter
MODE is given the value
. It indicates which positions are to be marked on the
screen using the marker type given by Parameter MARKER. It can take any of the following
"Initial" — The position of the cursor when the mouse button is pressed is marked.
"Fit" — The corresponding fit position is marked.
"Ellipse" — As "Fit" but it also plots an ellipse at the HWHM radii and orientation.
"None" — No positions are marked.
MARKER = INTEGER (Read)
This parameter is only accessed if Parameter MARK
TRUE. It specifies the type of marker with which each cursor position should be marked, and
should be given as an integer PGPLOT marker type. For instance,
0 gives a box,
1 gives a dot,
3 gives an asterisk,
7 gives a triangle. The value must be larger than or equal to
The mode in which the initial co-ordinates are to be
obtained. The supplied string can be one of the following values.
"Interface" — positions are obtained usingparameters POS, POS2–POS5.
"Cursor" — positions are obtained using the graphics cursor of the device specified by Parameter
"Catalogue" — positions are obtained from a positions list using Parameter INCAT.
"File" — positions are obtained from a text file using Parameter COIN.
The NDF structure containing the data array to be analysed. In cursor mode (see
Parameter MODE), the run-time default is the displayed data, as recorded in the graphics database. In
other modes, there is no run-time default and the user must supply a value.
A group of attribute settings describing the style to use when drawing the graphics
markers specified by Parameter MARK.
A comma-separated list of strings should be given in which each string is either
an attribute setting, or the name of a text file preceded by an up-arrow character
Such text files should contain further comma-separated lists which will be read and interpreted in the
same manner. Attribute settings are applied in the order in which they occur within the list, with later
settings overriding any earlier settings given for the same attribute.
Each individual attribute setting should be of the form:
is the name of a plotting attribute, and
is the value to assign to the attribute. Default values will be used for any unspecified attributes. All
attributes will be defaulted if a null value (
!)—the initial default—is supplied. To apply changes of
style to only the current invocation, begin these attributes with a plus sign. A mixture of persistent
and temporary style changes is achieved by listing all the persistent attributes followed by a plus sign
then the list of temporary attributes.
See Section E for a description of the available attributes. Any unrecognised attributes are
ignored (no error is reported).
POLAR = _LOGICAL (Read)
co-ordinates supplied through POS2–POS5 are interpreted in polar co-ordinates (offset, position
angle) about the primary beam. The radial co-ordinate is a distance measured in units of the
latitude axis if the current WCS Frame
is a SKY DOMAIN or the first axis for other Frames.
For a SKY current WCS Frame, position angle follows the standard convention of North
through East. For other Frames the angle is measured from the second axis anticlockwise,
for a PIXEL Frame it would be from y
through negative x
, not the standard x
FALSE, the co-ordinates are the regular axis co-ordinates in the current Frame.
POLAR is only accessed when there is more than one beam to fit.
POS = LITERAL (Read)
When MODE =
POS specifies the co-ordinates of the primary beam position. This is
either merely an initial guess for the fit, or if Parameter FIXPOS is
, it defines a fixed location. It
is specified in the current co-ordinate Frame of the NDF (supplying a colon
will display details
of the current co-ordinate Frame). A position should be supplied as a list of formatted
WCS axis values separated by spaces or commas, and should lie within the bounds of the
If the initial co-ordinates are supplied on the command line without BEAMS the number of
contiguous POS, POS2,…parameters specifies the number of beams to be fit. If the initial co-ordinates
are supplied on the command line without BEAMS specified only one beam will be fit.
When MODE =
these parameters specify the co-ordinates of the
secondary beam positions. These should lie within the bounds of the NDF. For each parameter the
supplied location may be merely an initial guess for the fit, or if Parameter FIXPOS is
, it defines a
fixed location, unless Parameter FIXSEP is
, whereupon it defines a fixed separation from the
For POLAR =
FALSE each distance should be given as a single literal string containing a space- or
comma-separated list of formatted axis values measured in the current co-ordinate Frame of the NDF.
The allowed formats depends on the class of the current Frame. Supplying a single colon
display details of the current Frame, together with an indication of the format required for each axis
value, and a new parameter value is then obtained.
If Parameter POLAR is
TRUE, POS2–POS5 may be given as an offset followed by a position angle. See
Parameter POLAR for more details of the sense of the angle and the offset co-ordinates.
The parameter name increments by 1 for each subsequent beam feature. Thus POS2 applies to the first
secondary beam (second position in all), POS3 is for the second secondary beam, and so on. As the
total number of parameters required is one fewer than the value of Parameter BEAMS,
POS2–POS5 are only accessed when BEAMS exceeds 1.
REFPOS = LITERAL (Read)
reference position. This is often the desired position for the beam. The offset of the primary
beam with respect to this point is reported and stored in Parameter REFOFF. It is only
accessed if the current WCS Frame in the NDF is not a SKY Domain containing a reference
The co-ordinates are specified in the current WCS Frame of the NDF (supplying a colon
display details of the current co-ordinate Frame). A position should be supplied either as a list of
formatted WCS axis values separated by spaces or commas. A null value (
!) requests that the centre of
the supplied map is deemed to be the reference position.
RESID = NDF (Write)
The map of the
residuals (data minus model) of the fit. It inherits the properties of the input NDF, except that its data
type is _DOUBLE or _REAL depending on the precision demanded by the type of IN, and no variance
is propagated. A null (
!) value requests that no residual map be created.
TITLE = LITERAL
The title for the NDF to contain the residuals of the fit. If null (
!) is entered the NDF will not
contain a title.
["KAPPA - BEAMFIT"]
VARIANCE = _LOGICAL (Read)
TRUE, then any
VARIANCE component present within the input NDF will be used to weight the fit; the
weight used for each data value is the reciprocal of the variance. If set to
FALSE or there is no
VARIANCE present, all points will be given equal weight.
AMP( 2 * BEAMS ) = _DOUBLE (Write)
The amplitude and its error for each beam.
BACK( 2 * BEAMS ) = _DOUBLE (Write)
The background level and its error at each beam
CENTRE( 2 * BEAMS ) = LITERAL (Write)
The formatted co-ordinates and their
errors of each beam in the current co-ordinate Frame of the NDF.
GAMMA( 2 * BEAMS )
= _DOUBLE (Write)
The shape exponent and its error for each beam.
* BEAMS ) = _DOUBLE (Write)
The major-axis FWHM and its error, measured in the
current co-ordinate Frame of the NDF, for each beam. Note that the unit for sky co-ordinate
Frames is radians.
MINFWHM( 2 * BEAMS ) = _DOUBLE (Write)
The minor-axis FWHM
and its error, measured in the current co-ordinate Frame of the NDF, for each beam. Note
that the unit for sky co-ordinate Frames is radians.
OFFSET( ) = LITERAL (Write)
formatted offset and its error of each secondary beam feature with respect to the primary beam.
They are measured in the current Frame of the NDF along a latitude axis if that Frame is
in the SKY Domain, or the first axis otherwise. The number of values stored is twice the
number of beams. The array alternates an offset, then its corresponding error, appearing in
beam order starting with the first secondary beam.
ORIENT( 2 * BEAMS ) = _DOUBLE
The orientation and its error, measured in degrees for each beam. If the current
is a SKY Frame, the angle is measured from North through East. For other
Frames the angle is from the x
-axis through y
PA() = _REAL (Write)
The position angle
and its errors of each secondary beam feature with respect to the primary beam. They are
measured in the current Frame of the NDF from North through East if that is a SKY Domain, or
anticlockwise from the y axis otherwise. The number of values stored is twice the number of
beams. The array alternates a position angle, then its corresponding error, appearing in
beam order starting with the first secondary beam.
REFOFF( 2 ) = LITERAL (Write)
The formatted offset followed by its error of the primary beam’s location with respect to
the reference position (see Parameter REFPOS). The offset might be used to assess the
optical alignment of an instrument. The ofset and its error are measured in the current
Frame of the NDF along a latitude axis if that Frame is in the SKY Domain, or the first axis
otherwise. The error is derived entirely from the uncertainities in the fitted position of the
primary beam, i.e. the reference position has no error attached to it. By definition the error is
zero when FIXPOS is
RMS = _REAL (Write)
The primary beam position’s root
mean-squared deviation from the fit.
SUM = _DOUBLE (Write)
The total data sum of
the multi-Gaussian fit above the background. The fit is evaluated at the centre of every
pixel in the input NDF (including bad-valued pixels). The fitted background level is then
removed from the fit value, and the sum of these is written to this output parameter.