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Knowledgebase: ALMA Observing Tool (OT)
How do I set up a mosaic in the OT?
Posted by John Hibbard, Last modified by Rein Warmels on 15 March 2017 03:44 PM

The OT has a built in utility to easily set up rectangular, equally spaced mosaics using the "1 rectangular Field" option in the "Field Setup" editor. This is the easiest way of setting up mosaics, since the sensitivity entered is that desired over the combined image, and the OT's time estimate takes into account the overlap between pointings. Also, the 12-m, 7-m and TP Array observations are automatically set up in the most efficient way possible (i.e. the 7-m pointings are spaced further apart to account for the larger beamsize, the TP observations will scan the entire area covered by the mosaic).

If your scientific needs are not met by this standard mosaic (e.g. a rectangular mosaic would be very inefficient or you need your pointings to be spaced unequally), you can instead define a custom mosaic using the "Individual Pointing(s)" option. In this case, you define one or multiple sources that contain a number of offset pointings to be processed together to give one image. In order for the 'Custom Mosaic' option to be allowed, the offset pointings must overlap, and all sources in that Science Goal must contain custom mosaics (it is not possible to mix offset pointings to be processed separately and custom mosaics within a single Science Goal). Here, the sensitivity entered is assumed to be per pointing and any overlap should be accounted for by the user. Also, any ACA observations will use exactly the same pointing centres as the 12-m Array and may oversample the mosaic.

For instructions on how to set up the two types of mosaic in the OT see the OT video tutorial 3: The Spatial Field Setup, or the OT Quickstart Guide. Both documents are available via the Science Portal Documention page.

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