# How are the days relating to right ascension around a polar star chart decided?

If you look at this link they have days realting to right acension.

How did they calculate nov 20th == 0h, dec 6 == 1h?

I was trying to calculate this in astropy, but I end up with nov 20th, 8pm == 22h.

from astropy import units as u
from astropy.time import Time
from astropy.coordinates import SkyCoord, EarthLocation, AltAz

time_str =  "2017-11-20 20:00"

#Greenville SC, eclipse just went through there.
LON =  -82.3940
LAT = 34.8526
loc = EarthLocation(lat=LAT*u.deg, lon=LON*u.deg, height=0*u.m)

utcoffset = -4*u.hour  # Eastern Daylight Time
obstime = Time(time_str,scale='utc') - utcoffset

cord = SkyCoord(alt=90*u.degree,az=0*u.degree,obstime=obstime,frame = 'altaz',location = loc)
print obstime,cord.fk5.ra.hour, cord.fk5.dec.deg

>> 2017-11-21 00:00:00.000 22.505946538 34.7569396915

• What are you actually trying to do? Aug 25 '17 at 23:07
• Want to make my own start chart, and understand how I should add a border with months around the chart. Aug 25 '17 at 23:56