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Field Center Coordinates
This panel is visible if Individual Pointing(s) has been selected in the Source panel. Up to 150 pointings can be defined per Science Goal, distributed between multiple sources. It is possible to define multiple pointings per source and these can either be mosaiced or processed as individual images, depending on the ``custom mosaic'' parameter. If the Total Power Array is required for a single pointing, each must go into a separate source definition.
- Custom Mosaic: If the pointings overlap and should be processed as a mosaic, select this option (set as default if individual pointing(s) is selected). If this is selected, the centre of each pointing must be a maximum of one antenna beamsize away from its nearest neighbour's centre. If custom mosaic is not selected, the observatory will deliver a separate image per pointing. If the project requires the Total Power Array, the OT will automatically calculate the TP scanning area and display this on the Visual Spatial Editor.
- PointingPattern: Enter the field centre in absolute or relative (offset) coordinates. Offsets are defined with respect to the source coordinate and are recommended.
- Offset Unit: Select the units for the offset.
- RA: Absolute coordinate of the centre of the pattern or the offset from the field centre in Right Ascension.
- DEC: Absolute coordinate of the centre of the pattern or the offset from the field centre in Declination.
At the bottom of the panel are buttons which allow a user to add and delete pointings manually, but also to import and export them from and to an external ASCII file. The file format is very flexible and allows a user to write out the pointing positions in either offset or absolute coordinates and will automatically do the conversion between the two i.e. one can export in a different system to what is displayed. An example of the format for absolute coordinates in sexagesimal is shown here:
RA , Dec, Coordinate Type, Coordinate Units
-- This signals end of the header
04:31:38.4369, 18:13:57.651,Absolute,SEXAGESIMAL
04:31:40.5426, 18:13:57.650,Absolute,SEXAGESIMAL
04:31:36.3312, 18:13:57.650,Absolute,SEXAGESIMAL
The ``Absolute'' coordinate type can be combined with the units ``SEXAGESIMAL'', ``DEGREES'' OR ``RADIANS'', whilst ``Offset'' pointings can be defined in ``ARCSECS'', ``ARCMIN'' or ``DEGREES''. The unit type must be capitalized, but this doesn't seem to be necessary for the coordinate type.
Figure 5.3:
The Field Centre Coordinates panel for the case of individual pointings.
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Next: Rectangle
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The ALMA OT Team, 2015 Sep 03