webbpsf_ext.coords.get_idl_offset¶

webbpsf_ext.coords.get_idl_offset(base_offset=(0, 0), dith_offset=(0, 0), base_std=0, use_ta=True, dith_std=0, use_sgd=True, rand_seed=None, **kwargs)[source]¶

Calculate pointing offsets in ‘idl’ coordinates with errors. Inputs come from the APT’s .pointing file. For a sequence of dithers, make sure to only calculate the base offset once, and all dithers independently. For instance:

>>> base_offset = get_idl_offset(base_std=None)
>>> dith0 = get_idl_offset(base_offset, dith_offset=(0,0), dith_std=None)
>>> dith1 = get_idl_offset(base_offset, dith_offset=(-0.01,+0.01), dith_std=None)
>>> dith2 = get_idl_offset(base_offset, dith_offset=(+0.01,+0.01), dith_std=None)
>>> dith3 = get_idl_offset(base_offset, dith_offset=(+0.01,-0.01), dith_std=None)
>>> dith4 = get_idl_offset(base_offset, dith_offset=(-0.01,-0.01), dith_std=None)

Parameters

base_offset (array-like) – Corresponds to (BaseX, BaseY) columns in .pointing file (arcsec).
dith_offset (array-like) – Corresponds to (DithX, DithY) columns in .pointing file (arcsec).
base_std (float or array-like or None) – The 1-sigma pointing uncertainty per axis for telescope slew. If None, then standard deviation is chosen to be either 5 mas or 100 mas, depending on use_ta setting.
use_ta (bool) – If observation uses a target acquisition, then assume only 5 mas of pointing uncertainty, other 100 mas for “blind” pointing.
dith_std (float or array-like or None) – The 1-sigma pointing uncertainty per axis for dithers. If None, then standard deviation is chosen to be either 2.5 or 5 mas, depending on use_sgd setting.
use_sgd (bool) – If True, then we’re employing small-grid dithers with the fine steering mirror, which has a ~2.5 mas uncertainty. Otherwise, assume standard small angle maneuver, which has ~5 mas uncertainty.