Plotting the brightest 200 stars

Here we try to replicate what we did previously in the Jupyter notebook?

import pandas as pd
import matplotlib.pyplot as plt
from math import pi
plt.style.use('seaborn-v0_8-darkgrid')

Then we can load in our data:

stars = pd.read_csv(
    './brightest_200.csv',
    header=None,
    names=['Official', 'Common', 'RA', 'DEC'])
stars

	Official	Common	RA	DEC
0	Alpha Canis Majoris	Sirius	06h45m	-16.7
1	Alpha Carinae	Canopus	06h24m	-52.7
2	Alpha Centauri	Rigil Kentaurus	14h40m	-60.8
3	Alpha Bo�tis	Arcturus	14h16m	19.2
4	Alpha Lyrae	Vega	18h37m	38.8
...	...	...	...	...
195	Delta Herculis	Sarin	17h15m	24.8
196	Kappa Centauri	Ke Kwan	14h59m	-42.1
197	Alpha Lyncis	NaN	09h21m	34.4
198	N Velorum	NaN	09h31m	-57.0
199	Pi Herculis	NaN	17h15m	36.8

200 rows × 4 columns

Our main task here is to get the Right Ascension values into a decimal form, so that we can meaningfully plot them. Writing a quick function to handle a single RA value:

def to_ra_deg(ra_str):
    hours = float(ra_str[:2])
    minutes = float(ra_str[3:5])
    return (hours + minutes/60) * 15 #15 deg per hour

Then we can apply it to create a new column:

stars['RA_deg'] = stars.RA.apply(to_ra_deg)
stars

	Official	Common	RA	DEC	RA_deg
0	Alpha Canis Majoris	Sirius	06h45m	-16.7	101.25
1	Alpha Carinae	Canopus	06h24m	-52.7	96.00
2	Alpha Centauri	Rigil Kentaurus	14h40m	-60.8	220.00
3	Alpha Bo�tis	Arcturus	14h16m	19.2	214.00
4	Alpha Lyrae	Vega	18h37m	38.8	279.25
...	...	...	...	...	...
195	Delta Herculis	Sarin	17h15m	24.8	258.75
196	Kappa Centauri	Ke Kwan	14h59m	-42.1	224.75
197	Alpha Lyncis	NaN	09h21m	34.4	140.25
198	N Velorum	NaN	09h31m	-57.0	142.75
199	Pi Herculis	NaN	17h15m	36.8	258.75

200 rows × 5 columns

And finally we can plot it up:

Suppose I wanted to highlight the star Betelgeuse:

b = stars[stars.Common == 'Betelgeuse']
b

	Official	Common	RA	DEC	RA_deg
9	Alpha Orionis	Betelgeuse	05h55m	7.4	88.75

And it was at this point that I realized that the projection is NOT working as I’d have expected. Turns out it wants radian values between -\(\pi\) and \(\pi\). Fair enough.

def convert(deg):
    rad = deg * pi / 180
    if rad > pi:
        rad -= 2 * pi
    return rad


plt.subplot(111, projection='aitoff')
plt.plot(
    stars.RA_deg.apply(convert), 
    stars.DEC.apply(convert), '.')
plt.plot(
    b.RA_deg.apply(convert), 
    b.DEC.apply(convert), '.')
plt.show()

Still kinda hard to see Orion, as it is mirrored, but it is at least visible in the correct region now.