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Rectangle
This panel is only visible when ``1 Rectangular Field'' is selected in the Source panel. It is possible to define multiple sources, each of which uses a rectangular field pattern. To do this, one must start with only a single source in the Science Goal. This can be set up as a rectangular mosaic and any further sources that are defined will be forced to use rectangular field patterns.
For each rectangle, the OT will calculate a mosaic pattern for the 12- and 7-m Arrays based on the spacing parameter. A larger version of the user-drawn rectangle will be used for raster scanning with the TP Array. A total of 150 12-m Array pointings is allowed, summed over all rectangles.
- Coords Type: Field centre in absolute or relative coordinates. Relative positions are offset from the source coordinate and are recommended. Absolute coordinates can be entered, but will be converted to offsets from the source coordinate during SB generation as absolute coordinates cannot be used with the telescope control system.
- Field Centre Coordinates (Relative)
- Offset(Longitude): Longitudinal offset of the centre of the rectangle from the source coordinate.
- Offset(latitude): Latitudinal offset of the centre of the rectangle from the source coordinate.
- Field Centre Coordinates (Absolute)
- System: The system used for the coordinates. This should be set to ICRS.
- Sexagesimal display?: View the coordinates in sexagesimal or decimal degrees.
- RA: The central R.A. coordinate of the rectangle.
- DEC: The central Declination coordinate of the rectangle.
- p length: Length of one side of the rectangle. For a rectangle with zero rotation, this refers to the horizontal axis.
- q length: Length of the other side of the rectangle.
- Position Angle: Position angle (North through East) of the ``p'' side of the rectangle from the vertical direction.
- Spacing: Distance between mosaic pointings. This can be specified in arcsec or in fraction of the antenna beamsize, the latter being the default. Nyquist spacing (
where
is the antenna diameter) is assumed and should usually be selected, unless the sources being observed are relatively small. The spacing is usually shown as a fraction of the antenna beamsize (
) and thus in these units is approximately equal to 0.51. If Nyquist sampling is not used, the reasons for this should be given in the Technical Justification node, but values between 0.7 and 0.8 are fairly typical for observing wide-fields of relatively small sources. A button is provided to reset to the Nyquist value.
The number of pointings calculated by the OT is displayed, for the 12-m and (if required based on the Control & Performance parameters) 7-m Arrays. A button is provided to export the pointings (12-m and 7-m Array) to an ASCII file on disk. If desired, this can be used as the basis of a set of individual pointings that can be read into the Field Source.
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The ALMA OT Team, 2016 Aug 23