astLib.astWCS.WCS

Package astLib :: Module astWCS :: Class WCS |
[hide private]
[frames] | no frames]

# Class WCS

source code

This class provides methods for accessing information from the World Coordinate System (WCS) contained in the header of a FITS image. Conversions between pixel and WCS coordinates can also be performed.

To create a WCS object from a FITS file called "test.fits", simply:

WCS=astWCS.WCS("test.fits")

Likewise, to create a WCS object from the pyfits.header of "test.fits":

img=pyfits.open("test.fits") header=img[0].header WCS=astWCS.WCS(header, mode = "pyfits")

Instance Methods | [hide private]
__init__(self, headerSource, extensionName=0, mode="image", zapKeywords=[]) Creates a WCS object using either the information contained in the header of the specified .fits image, or from a pyfits.header object. | source code
astWCS.WCS object |
copy(self) Copies the WCS object to a new object. | source code
updateFromHeader(self) Updates the WCS object using information from WCS.header. | source code
list |
getCentreWCSCoords(self) Returns the RA and dec coordinates (in decimal degrees) at the centre of the WCS. | source code
list |
getFullSizeSkyDeg(self) Returns the width, height of the image according to the WCS in decimal degrees on the sky (i.e., with the projection taken into account). | source code
list |
getHalfSizeDeg(self) Returns the half-width, half-height of the image according to the WCS in RA and dec degrees. | source code
list |
getImageMinMaxWCSCoords(self) Returns the minimum, maximum WCS coords defined by the size of the parent image (as defined by the NAXIS keywords in the image header). | source code
list |
wcs2pix(self, RADeg, decDeg) Returns the pixel coordinates corresponding to the input WCS coordinates (given in decimal degrees). | source code
list |
pix2wcs(self, x, y) Returns the WCS coordinates corresponding to the input pixel coordinates. | source code
bool |
coordsAreInImage(self, RADeg, decDeg) Returns True if the given RA, dec coordinate is within the image boundaries. | source code
float |
getRotationDeg(self) Returns the rotation angle in degrees around the axis, North through East. | source code
int |
isFlipped(self) Returns 1 if image is reflected around axis, otherwise returns 0. | source code
float |
getPixelSizeDeg(self) Returns the pixel scale of the WCS. | source code
float |
getXPixelSizeDeg(self) Returns the pixel scale along the x-axis of the WCS in degrees. | source code
float |
getYPixelSizeDeg(self) Returns the pixel scale along the y-axis of the WCS in degrees. | source code
float |
getEquinox(self) Returns the equinox of the WCS. | source code
float |
getEpoch(self) Returns the epoch of the WCS. | source code

Method Details | [hide private]

### __init__(self, headerSource, extensionName=0, mode="image", zapKeywords=[]) (Constructor) | source code
Creates a WCS object using either the information contained in the header of the specified .fits image, or from a pyfits.header object. Set mode = "pyfits" if the headerSource is a pyfits.header. For some images from some archives, particular header keywords such as COMMENT or HISTORY may contain unprintable strings. If you encounter this, try setting zapKeywords = ['COMMENT', 'HISTORY'] (for example). Parameters: `headerSource` (string or pyfits.header) - filename of input .fits image, or a pyfits.header object `extensionName` (int or string) - name or number of .fits extension in which image data is stored `mode` (string) - set to "image" if headerSource is a .fits file name, or set to "pyfits" if headerSource is a pyfits.header object `zapKeywords` (list) Note: The meta data provided by headerSource is stored in WCS.header as a pyfits.header object.

### copy(self) | source code
Copies the WCS object to a new object. Returns: astWCS.WCS object WCS object

### updateFromHeader(self) | source code
Updates the WCS object using information from WCS.header. This routine should be called whenever changes are made to WCS keywords in WCS.header.

### getCentreWCSCoords(self) | source code
Returns the RA and dec coordinates (in decimal degrees) at the centre of the WCS. Returns: list coordinates in decimal degrees in format [RADeg, decDeg]

### getFullSizeSkyDeg(self) | source code
Returns the width, height of the image according to the WCS in decimal degrees on the sky (i.e., with the projection taken into account). Returns: list width and height of image in decimal degrees on the sky in format [width, height]

### getHalfSizeDeg(self) | source code
Returns the half-width, half-height of the image according to the WCS in RA and dec degrees. Returns: list half-width and half-height of image in R.A., dec. decimal degrees in format [half-width, half-height]

### getImageMinMaxWCSCoords(self) | source code
Returns the minimum, maximum WCS coords defined by the size of the parent image (as defined by the NAXIS keywords in the image header). Returns: list [minimum R.A., maximum R.A., minimum Dec., maximum Dec.]

### wcs2pix(self, RADeg, decDeg) | source code
Returns the pixel coordinates corresponding to the input WCS coordinates (given in decimal degrees). RADeg, decDeg can be single floats, or lists or numpy arrays. Returns: list pixel coordinates in format [x, y]

### pix2wcs(self, x, y) | source code
Returns the WCS coordinates corresponding to the input pixel coordinates. Returns: list WCS coordinates in format [RADeg, decDeg]

### coordsAreInImage(self, RADeg, decDeg) | source code
Returns True if the given RA, dec coordinate is within the image boundaries. Returns: bool True if coordinate within image, False if not.

### getRotationDeg(self) | source code
Returns the rotation angle in degrees around the axis, North through East. Returns: float rotation angle in degrees

### isFlipped(self) | source code
Returns 1 if image is reflected around axis, otherwise returns 0. Returns: int 1 if image is flipped, 0 otherwise

### getPixelSizeDeg(self) | source code
Returns the pixel scale of the WCS. This is the average of the x, y pixel scales. Returns: float pixel size in decimal degrees

### getXPixelSizeDeg(self) | source code
Returns the pixel scale along the x-axis of the WCS in degrees. Returns: float pixel size in decimal degrees

### getYPixelSizeDeg(self) | source code
Returns the pixel scale along the y-axis of the WCS in degrees. Returns: float pixel size in decimal degrees

### getEquinox(self) | source code
Returns the equinox of the WCS. Returns: float equinox of the WCS

### getEpoch(self) | source code
Returns the epoch of the WCS. Returns: float epoch of the WCS