Last modified: 13 December 2018

Why do I get a parse error with this region file?

# Region file format: CIAO version 1.0	
-rotbox(4055.375,4165.5674,4.6747966,4.4715447,63.400002)
annulus(4059.5601,4163.4399,2.0325203,7.113821)

The software processes the shapes in the order listed, so CIAO attempts to exclude the rotbox shape from an area that is not defined. The field() region, which defines the entire field of view, can be added to the beginning of the region file to avoid syntax errors:

# Region file format: CIAO version 1.0
field()
-rotbox(4055.375,4165.5674,4.6747966,4.4715447,63.400002)
annulus(4059.5601,4163.4399,2.0325203,7.113821)

Note that the order of the regions does matter; if you intend for the box to be excluded from the annulus:

# Region file format: CIAO version 1.0
field()
annulus(4059.5601,4163.4399,2.0325203,7.113821)
-rotbox(4055.375,4165.5674,4.6747966,4.4715447,63.400002)

See the Using CIAO Region Files thread and ahelp dmregions for more information.