Topocentric example on homepage throws error(?)

[haggletonpie]

http://rhodesmill.org/skyfield/

When running the 2nd example to compute the apparent position of Mars when viewed from Boston at time t, skyfield gripes about "plussing" the earth body and the Topos for Boston.

TypeError: unsupported operand type(s) for +: 'Body' and 'Topos'

Surely, I'm missing something...?

#====the first example====
#works fine

from skyfield.api import load

planets = load('de421.bsp')
earth, mars = planets['earth'], planets['mars']

ts = load.timescale()
t = ts.now()
astrometric = earth.at(t).observe(mars)
ra, dec, distance = astrometric.radec()

print(ra)
print(dec)
print(distance)

#====appended 2nd example====
#throws type/operand error

from skyfield.api import Topos

boston = earth + Topos('42.3583 N', '71.0636 W')
astrometric = boston.at(t).observe(mars)
alt, az, d = astrometric.apparent().altaz()

print(alt)
print(az)

[brandon-rhodes]

You could be using a very old version of Skyfield — what version do you have installed?

pip freeze| grep skyfield

[haggletonpie]

Thanks.

pip install skyfield --upgrade

Great library. Thanks much.

[brandon-rhodes]

I'm glad it's working for you now! :)