18.39 UV_SHIFT

[CLEAN\]UV_SHIFT [CenterX CenterY UNIT] [ANGLE Angle] [/FILE FileInOut]

Shift the current (if no /FILE option is present) or specified (if the /FILE option is here) UV table (single field or mosaic) to a common phase center and/or rotate it.

Angle is desired position angle of the Celestial North from the Y axis (counted positive towards East, i.e. counter-clockwise in usual astronomical images), in Degree. It is thus an absolute value.

If UNIT is ABSOLUTE, CenterX and CenterY are absolute coordinates in usual sexagesimal notation.

If not, CenterX and CenterY are offsets in the specified angular unit (SECOND, MINUTE, DEGREE or RADIAN).

Although UV_MAP also provides a direct possibility to re-center the image on a specified projection (phase) center cmobined with a rotation of the main axes, the modified visibilities cannot be saved on file. It is sometimes required to do this for specific use. UV_SHIFT provides this possibility, and the shifted UV table can be written using command WRITE UV.

UV_DEPROJECT includes the UV_SHIFT capabilities, but also has additional functions, and a different syntax.