def sky_offset(self, ra_offset, dec_offset):
"""
Update header keywords to simulate a shift in telescope pointing.
Parameters
----------
ra_offset: float
Shift in RA (arcseconds)
dec_offset: float
Shift in declination (arcseconds)
"""
self.phu['RAOFFSET'] += ra_offset
self.phu['DECOFFSE'] += dec_offset
# XOFFSET, YOFFSET
xoffset, yoffset = self._xymapping(ra_offset, dec_offset)
self.phu['XOFFSET'] += xoffset
self.phu['YOFFSET'] += yoffset
# POFFSET. QOFFSET
poffset, qoffset = self._pqmapping(ra_offset, dec_offset)
self.phu['POFFSET'] += poffset
self.phu['QOFFSET'] += qoffset
# WCS matrix
for ext in self:
ext.hdr['CRVAL1'] += ra_offset / (3600. * cosd(self.dec()))
ext.hdr['CRVAL2'] += dec_offset / 3600.
ext.wcs = adwcs.fitswcs_to_gwcs(ext.hdr)
def rotate(self, angle):
"""
Modify the CD matrices of all the headers to effect a rotation.
This assumes that the CRVALi keywords are the same in all headers
or else this modification may be inconsistent.
Parameters
----------
angle: float
Rotation angle (degrees)
"""
for ext in self:
cd_matrix = models.Rotation2D(angle)(*WCS(ext.hdr).wcs.cd)
ext.hdr.update({
'CD{}_{}'.format(i + 1, j + 1): cd_matrix[i][j]
for i in (0, 1) for j in (0, 1)
})
ext.wcs = adwcs.fitswcs_to_gwcs(ext.hdr)
self.phu['PA'] = (self.phu.get('PA', 0) + angle) % 360
def add_extension(self,
data=None,
shape=None,
dtype=np.float32,
pixel_scale=None,
flip=False,
extra_keywords={}):
"""
Add an extension to the existing AD, with some basic header keywords.
Parameters
----------
data: array/None
data to add; if None, add zeros of specified shape
shape: tuple/None
dimensions of .data plane; if None, will use the shape of the
first extension (ignored if data is not None)
dtype: datatype
datatype of data if data is None
pixel_scale: float/None
pixel scale for this plane; if None, use the descriptor value
flip: bool
if True, flip the WCS (so East is to the right if North is up)
extra_keywords: dict
extra keywords to put in this extension's Header
"""
# If no shape is provided, use the first extension's shape
if data is None:
if shape is None and len(self) > 0:
shape = self[0].nddata.shape
elif shape is None:
raise ValueError("Must specify a shape if data is None")
self.append(np.zeros(shape, dtype=dtype))
else:
self.append(data)
shape = data.shape
extver = len(self)
shape_value = '[1:{1},1:{0}]'.format(*shape)
self[-1].hdr.update({
'EXTNAME': 'SCI',
'EXTVER': extver,
self._keyword_for('data_section'): shape_value,
self._keyword_for('detector_section'): shape_value,
self._keyword_for('array_section'): shape_value
})
self[-1].hdr.update(extra_keywords)
# For instruments with multiple extensions, the relationship between
# the WCS keywords on the extenstions has to be handled at the
# instrument level. Here we just deal with the case of creating the
# first extension and put the fiducial point in the middle.
if len(self) == 1 and 'RA' in self.phu and 'DEC' in self.phu:
self[-1].hdr.update({
'CRVAL1': self.phu['RA'],
'CRVAL2': self.phu['DEC'],
'CTYPE1': 'RA---TAN',
'CTYPE2': 'DEC--TAN',
'CRPIX1': 0.5 * (shape[-1] + 1),
'CRPIX2': 0.5 * (shape[-2] + 1)
})
if pixel_scale is None:
pixel_scale = self.pixel_scale()
pa = self.phu.get('PA', 0)
if pixel_scale is not None:
cd_matrix = models.Rotation2D(angle=pa)(
*np.array([[pixel_scale if flip else -pixel_scale, 0],
[0, pixel_scale]]) / 3600.0)
self[-1].hdr.update({
'CD{}_{}'.format(i + 1, j + 1): cd_matrix[i][j]
for i in (0, 1) for j in (0, 1)
})
self[-1].wcs = adwcs.fitswcs_to_gwcs(self[-1].hdr)