Question

I’d like to learn how to grab information from a FITS file header and transfer that information to an ascii table. For example, this is how I would obtain the info.:

import pyfits
a = pyfits.open('data.fits')
header = a[0].header # Which should return something like this (It is  BinHDUlist)
SIMPLE  =                T / conforms to FITS standards                    
                               / institution responsible for creating this file 
TELESCOP= 'Kepler  '           / telescope                                      
INSTRUME= 'Kepler Photometer'  / detector type                                  
OBJECT  = 'KIC 8631743'        / string version of KEPLERID                     
RA_OBJ  =           294.466516 / [deg] right ascension                          
DEC_OBJ =            44.751131 / [deg] declination                              

How could I create an ASCII table that contains RA_OBJ and DEC_OBJ ?

EDIT: I’d like to create a .dat file that contains two columns (RA and DEC) from the headers. Here is an example of what I am trying:

import asciitable
import asciidata
import pyfits
import numpy as np

# Here I have taken all the fits files in my current directory and did the following:
# ls > z.txt so that all the fits files are in one place.

a = asciidata.open('z.txt')
i = 0 #There are 371 fits files in z.txt
while i<=370:
    b = pyfits.open(a[0][i])
    h = b[0].header
    RA = np.array([h['RA_OBJ']])
    DEC = np.array(h['DEC_OBJ']])
    asciitable.write({'RA': RA, 'DEC': DEC}, 'coordinates.dat', names=['RA', 'DEC'])
    i = i+1

I’d like for this to write a .dat file containing something like this:

RA    DEC
###   ###
...   ...
...   ...
...   ...

Instead, my code just writes over the keys of the previous files. Any ideas?

Answer 1

I think you might benefit from reading the pyfits documentation more carefully. The header attribute is a pyfits.header.Header object, which is a dictionary-like object. So you can do something like:

import pyfits

keys = ['SIMPLE', 'TELESCOP', 'INSTRUME', 'OBJECTS', 'RA_OBJ', 'DEV_OBJ']

hdulist = pyfits.open("data.fits")
header = hdulist[0].header
for k in keys:
    print k, "=", header[k]

You can add more fancy outputting, put the resulting string in variable, checking for missing keys, etc.

EDIT:

Here’s how this could be coupled with asciitable and numpy:

import asciitable
import numpy as np

keys = ['RA', 'DEC']
data = {}

# Initialize "data" with empty lists for each key
for k in keys:
    data[k] = []

# Collect all data in the "data" dictionary
for i in range(0, 50):
    data['RA'].append(np.array(i))
    data['DEC'].append(np.array(i+1))

asciitable.write(data, "coords.dat", names=keys)