code: def find_gsc_offset(image, input_catalog='GSC1', output_catalog='GAIA'):
      
      serviceType = "GSCConvert/GSCconvert.aspx"
      spec_str = "TRANSFORM={}-{}&IPPPSSOOT={}"
  
      if 'rootname' in pf.getheader(image):
          ippssoot = pf.getval(image, 'rootname').upper()
      else:
          ippssoot = fu.buildNewRootname(image).upper()
  
      spec = spec_str.format(input_catalog, output_catalog, ippssoot)
      serviceUrl = "{}/{}?{}".format(SERVICELOCATION, serviceType, spec)
      rawcat = requests.get(serviceUrl)
      if not rawcat.ok:
          log.info("Problem accessing service with:\n{{}".format(serviceUrl))
          raise ValueError
  
      delta_ra = delta_dec = None
      tree = BytesIO(rawcat.content)
      for _, element in etree.iterparse(tree):
          if element.tag == 'deltaRA':
              delta_ra = float(element.text)
          elif element.tag == 'deltaDEC':
              delta_dec = float(element.text)
  
      return delta_ra, delta_dec
docs: Find the GSC to GAIA offset based on guide star coordinates
  
      Parameters
      ----------
      image : str
          Filename of image to be processed.
  
      Returns
      -------
      delta_ra, delta_dec : tuple of floats
          Offset in decimal degrees of image based on correction to guide star
          coordinates relative to GAIA.