%matplotlib inline
from __future__ import division

# Import of the PyEphem package
import ephem

from astropy.coordinates import SkyCoord

#This removes some nasty deprecation warnings that do not interfere with the execution
import warnings
warnings.filterwarnings('ignore')

# This IPython magic generates a table with version information
#https://github.com/jrjohansson/version_information
%load_ext version_information
%version_information ephem, astropy

# Let's define the equatorial coordinates of an object
eq=ephem.Equatorial('13:24:42.5','-60:15:59.4')

# The values are internally stored in radians
eq.ra, eq.dec, eq.epoch

# However they are printed as strings
print eq.ra, '\t', eq.dec, '\t', eq.epoch

# We can get a tuple (ra,dec) by using the get() method
print eq.get()

# To find the constellation corresponding to a coordinate tuple:
ephem.constellation((eq.ra,eq.dec))

eq50=ephem.Equatorial('13:24:42.5','-60:15:59.4',epoch=ephem.B1950)
print eq50.ra, '\t', eq50.dec, '\t', eq50.epoch

# Definition of the galactic coordinates of an object
ga=ephem.Galactic('1:59:55.9','+89:59:59.9')   
print ga.lon, ga.lat

# Longitude and latitude are returned by the get() method. They are shown in radians
print ga.get()

# Conversion of equatorial coordinates between epochs
eq1 = eq=ephem.Equatorial('13:24:42.5','-60:15:59.4')
eq2 = ephem.Equatorial(eq1,epoch=ephem.B1950)
print eq1.get()
print eq2.get()

# Conversióo from galactic to equatorial coordinates
# (we can in fact omit to declare the epoch, J2000 by default)
ga1 = ephem.Galactic('0','90',epoch=ephem.J2000)
eq1 = ephem.Equatorial(ga1)
print eq1.ra, eq1.dec

# Whirlpool Galaxy
SkyCoord.from_name("M51")    # "icrs" es la opción por defecto

# We can as well use other names for the same galaxy
SkyCoord.from_name('NGC 5194')

# The same object in galactic coordinates
SkyCoord.from_name("M51", frame='galactic')

c = SkyCoord.from_name("M51", frame='galactic')
# longitude and latitude can be accessed internally with c.l y c.b
# The internal representation of the angles is in degrees 
# However, these values can not be operated directly
c.l, c.b

# angles in radians
print c.l.radian, c.b.radian

# Angles in degrees
print c.l.degree, c.b.degree

# Arithmetic operation example
c.l.degree + 90

c = SkyCoord.from_name("M51", frame='icrs')

# Prints a string representation unfit to operate with
print c

# provides a tuple "hours", "minutes", "seconds"
print c.ra.hms

# Values in degrees
print c.dec.degree

# Of course they can be expressed in other types of units
print c.ra.radian, c.dec.radian

# ICRS coordinates
c = SkyCoord.from_name("M51", frame='icrs')

# FK5 coordinates
c5 = SkyCoord.from_name("M51", frame='fk5')

# In this example you can see the similarity between the two
print 'ICRS coordinates: ',c.ra.hms, c.dec.degree
print 'FK5 coordinates: ', c5.ra.hms, c5.dec.degree


# Let's obtain the galactic coordinates of a star
# We chose a southern hemisphere star

c = SkyCoord.from_name('Achernar', frame='galactic')
c

# Let's turn to FK5 equatorial coordinates:
c.fk5

# Conversely, from the ICRS obtain the galactic coordinates:
c = SkyCoord.from_name('Achernar', frame='icrs')
c.galactic