Convertir tiempo UTC a GMST (Tiempo Sideral Medio de Greenwich) en Python

 -*- coding: utf-8 -*-
"""
Created on Tue Oct 27 18:37:49 2015

@author: Rodolfo Escobar et al
"""
from datetime import datetime
from astropy.time import Time
from numpy import floor

# Reductor de rango 0-24h
def to24(x):
 while x >= 24:
  if x < 0:   
   x = x + 24
  if x > 24:
   x = x - 24
 return x
#

# Conversor de formato de hora
def tohms(x):
 time_hours = x
 time_minutes = time_hours * 60
 time_seconds = time_minutes * 60

 horas    = int(floor(time_hours))
 minutos  = int(floor(time_minutes % 60))
 segundos = int(floor(time_seconds % 60))
 return (horas,minutos,segundos)
#

#Programa principal
ut = Time(datetime.utcnow(), scale='utc')
JD= ut.jd # Fecha Juliana
D = JD - 2451545.0
GMST = 18.697374558 + 24.06570982441908*D
GMST = to24(GMST)
(horas,minutos,segundos) = tohms(GMST)
#

print "Hora Sideral:","{h}:{m}:{s}".format(h=horas, m=minutos, s=segundos)

Referencias:
Approximate Sidereal Time, USNO
Local Sidereal Time, Durham University
Astronomy With Your Personal Computer, Peter Duffett-Smith
Astropy.org