obs_strategies

ChopNodCombiner

Creates and combines 4 images for each of the chop/nod positions.

  • AA : original position (dx, dy) = (0, 0)

  • AB : chop position (dx, dy) = chop_offsets

  • BA : nod position (dx, dy) = nod_offsets

  • BB : chop-nod position (dx, dy) = nod_offsets + chop_offsets

Images are combined using:

im_combined = (AA - AB) - (BA - BB)

If no nod_offset is given, it is set to the inverse of chop_offset.

ChopNodCombiner is a detector effect and should be placed last in the

detector yaml (after the noise effects).

Keyword Arguments

chop_offsetstuple, optional

[arcsec] (dx, dy) offset of chop position relative to AA

nod_offsetstuple, optional

[arcsec] (dx, dy) offset of nod position relative to AA

Example yaml entry

name: perpendicular_chop_nod_slanted_pattern
description: chop throw to (+5, 0) and nod throw to (-7, +10) arcsec
class: ChopNodCombiner
include: True
kwargs:
    pixel_scale : "!INST.pixel_scale"
    chop_offsets : (5, 0)
    nod_offsets : (-7, 10)