JWST NIRCam mosaics are used primarily to cover areas larger than the 5.1' × 2.2' NIRCam field of view.
JWST mosaics may be used in NIRCam imaging and wide field slitless spectroscopy observations. The primary purpose is to cover areas larger than the 5.1' × 2.2' NIRCam Field of View. The spatial extent of each tile with zero overlap is 5.115033' × 2.221150' (the horizontal and vertical extent of the NIRCam aperture "ALL"). This spacing may be decreased (to make the pointings overlap, as is the default) or increased (to widen the gaps between pointings). By default, spacing is defined along NIRCam's "ALL" aperture axis, which is roughly aligned with the JWST (V2, V3) coordinate system and the NIRCam detector rows and columns. Optionally, shifts may be added between rows and/or columns to skew the pattern; these are input as rotation angles in the APT mosaic planning. All dithers and filter changes are performed at each pointing (or tile) in the mosaic before proceeding to the next.
To obtain roughly even observing depth over large areas, consider using the NIRCam "FULL" primary dither patterns in conjunction with mosaics with tile spacings of 5.8' × 2.25'.
JWST User Documentation Home
NIRCam Dithers and Mosaics
NIRCam Field of View
NIRCam Primary Dithers
NIRCam Wide Field Slitless Spectroscopy