rd2xy

drizzlepac.skytopix.rd2xy(input, ra=None, dec=None, coordfile=None, colnames=None, precision=6, output=None, verbose=True)

Primary interface to perform coordinate transformations from

pixel to sky coordinates using STWCS and full distortion models read from the input image header. Input positions must be in the form of RA/Dec strings or as columns in a coordinate file.

Parameters:

inputstr

Full filename with path of input image, an extension name [‘sci’,1] should be provided if input is a multi-extension FITS file

rastring or list or array, optional

RA from input image for a single or multiple positions (with or without ':') like '19:10:50.337406303' or '19 10 50.337406303'

decstring or list or array, optional

Dec from input image for a single or multiple positions (with or without ':') like '-60:2:22.186557409' or '-60 2 22.186557409'

coordfilestr, optional

Full filename with path of file with sky coordinates

colnamesstr, optional

Comma separated list of column names or list of column name strings from ‘coordfile’ files containing sky coordinates, respectively. This parameter will default to first two columns if None are specified. Column names for ASCII files will use ‘c1’,’c2’,… convention. Valid syntax: [‘c1’,’c3’] or ‘c1,c3’

separatorstr, optional

Non-blank separator used as the column delimiter in the coords file

precisionint, optional

Number of floating-point digits in output values

outputstr, optional

Name of output file with results, if desired

verbosebool

Print out full list of transformation results (default: False)

Returns:

xfloat or array

X position of pixel. If more than 1 input value, then it will be a numpy array.

yfloat or array

Y position of pixel. If more than 1 input value, then it will be a numpy array.

Notes

This module performs a full distortion-corrected coordinate transformation based on all WCS keywords and any recognized distortion keywords from the input image header.

Examples

1. The following command will transform the position 00:22:36.79 -72:4:9.0 into a position on the image ‘input_flt.fits[sci,1]’ using:

>>> from drizzlepac import skytopix
>>> x,y = skytopix.rd2xy("input_file_flt.fits[sci,1]", "00:22:36.79", "-72:4:9.0")

2. The set of sky positions from ‘input_flt.fits[sci,1]’ stored as the 3rd and 4th columns from the ASCII file ‘radec_sci1.dat’ will be transformed and written out to ‘xy_sci1.dat’ using:

>>> from drizzlepac import skytopix
>>> x,y = skytopix.rd2xy("input_flt.fits[sci,1]", coordfile='radec_sci1.dat',
...                     colnames=['c3','c4'], output="xy_sci1.dat")