Mimic the healpy header keywords.

def header_odict(nside,nest=False,coord=None, partial=True):
    """Mimic the healpy header keywords."""
    hdr = odict([])
    hdr['PIXTYPE']=odict([('name','PIXTYPE'),
                          ('value','HEALPIX'),
                          ('comment','HEALPIX pixelisation')])

    ordering = 'NEST' if nest else 'RING'
    hdr['ORDERING']=odict([('name','ORDERING'),
                           ('value',ordering),
                           ('comment','Pixel ordering scheme, either RING or NESTED')])
    hdr['NSIDE']=odict([('name','NSIDE'),
                        ('value',nside),
                        ('comment','Resolution parameter of HEALPIX')])
    if coord:
        hdr['COORDSYS']=odict([('name','COORDSYS'), 
                               ('value',coord), 
                               ('comment','Ecliptic, Galactic or Celestial (equatorial)')])
    
    if not partial:
        hdr['FIRSTPIX']=odict([('name','FIRSTPIX'),
                               ('value',0), 
                               ('comment','First pixel # (0 based)')])
        hdr['LASTPIX']=odict([('name','LASTPIX'),
                              ('value',hp.nside2npix(nside)-1),
                              ('comment','Last pixel # (0 based)')])
    hdr['INDXSCHM']=odict([('name','INDXSCHM'),
                           ('value','EXPLICIT' if partial else 'IMPLICIT'),
                           ('comment','Indexing: IMPLICIT or EXPLICIT')])
    hdr['OBJECT']=odict([('name','OBJECT'), 
                         ('value','PARTIAL' if partial else 'FULLSKY'),
                         ('comment','Sky coverage, either FULLSKY or PARTIAL')])
    return hdr