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Rectangle
This panel is only visible when ``1 Rectangular Field'' is selected in the Source panel. A recent change to the OT is that it is now 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 have not been demonstrated to work at the telescope).
- Field Centre Coordinates (Absolute)
- System: Coordinate System. FK5 J2000 is currently the only option that should be used.
- Sexagesimal display?: View the coordinates in sexagesimal or decimal degrees.
- RA: The centre coordinate of the rectangle in Right Ascension.
- DEC: The centre coordinate of the rectangle in Declination.
- Field Centre Coordinates (Relative)
- Offset(Longitude): Longitude offset of the centre of the rectangle from the source coordinate.
- Offset(latitude): Latitude offset of the centre of the rectangle from the source coordinate.
- 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. 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.
Figure 5.4:
The Rectangle panel of a Science Goal's Field Setup.
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The ALMA OT Team, 2015 Sep 03