WCS User Tools

grid_from_bounding_box is a function which returns a grid of input points based on the bounding_box of the WCS.

>>> from gwcs.wcstools import grid_from_bounding_box
>>> bounding_box = ((0, 4096), (0, 2048))
>>> x, y = grid_from_bounding_box(bounding_box)
>>> ra, dec = w(x, y)   

The wcstools module contains functions of general usability.

wcs_from_fiducial is a function which given a fiducial in some coordinate system, returns a WCS object.

>>> from gwcs.wcstools import wcs_from_fiducial
>>> from astropy import coordinates as coord
>>> from astropy import units as u
>>> from astropy.modeling import models

To create a WCS from a pointing on the sky, as a minimum pass a sky coordinate and a projection to the function.

>>> fiducial = coord.SkyCoord(5.46 * u.deg, -72.2 * u.deg, frame='icrs')
>>> tan = models.Pix2Sky_TAN()

Any additional transforms are prepended to the projection and sky rotation.

>>> trans = models.Shift(-2048) & models.Shift(-1024) | models.Scale(1.38*10**-5) & models.Scale(1.38*10**-5)
>>> w = wcs_from_fiducial(fiducial, projection=tan, transform=trans)
>>> w(2048, 1024)  
    (5.46, -72.2)