A couple weeks ago I wrote about how H. A. Rey introduced a new way of looking at the constellations, making them look more like their names. That post used Leo as an example. This post looks at Boötes (The Herdsman) [1].

Here is the constellation using the connections indicated in the IAU star chart.

Here is the constellation using the connections drawn in Rey’s book [2].

Rey’s version adds two stars, highlighted in red, but mostly connects the same stars in a different way. I suppose the herdsman is standing in the IAU version; it’s hard to tell. In Rey’s version, the huntsman is clearly seated and smoking a pipe. This is easier to see if we rotate the image a bit.

Here’s a comparison of the two interpretations side-by-side.

Here is the Python code that produced the two images. It’s a little cleaner than the code in the earlier post, and it draws larger dots to represent brighter stars.

import matplotlib.pyplot as plt

# data from https://en.wikipedia.org/wiki/List_of_stars_in_Bo%C3%B6tes

α = (14 + 16/60, 19 + 11/60, 0.0)  
β = (15 +  2/60, 40 + 23/60, 3.5)  
γ = (14 + 32/60, 38 + 18/60, 3.0)  
δ = (15 + 16/60, 33 + 19/60, 3.5)  
ε = (14 + 45/60, 27 +  4/60, 2.3)  
ζ = (14 + 41/60, 13 + 44/60, 3.8)  
η = (13 + 55/60, 18 + 24/60, 4.5)  
θ = (14 + 25/60, 51 + 51/60, 4.0)  
κ = (14 + 13/60, 51 + 47/60, 4.5)  
λ = (14 + 16/60, 46 +  5/60, 4.2)
μ = (15 + 24/60, 37 + 23/60, 4.3)
υ = (13 + 49/60, 15 + 48/60, 4.0)  
τ = (13 + 47/60, 17 + 27/60, 4.5)  
ρ = (14 + 32/60, 30 + 22/60, 3.6)  
    
k = -15 # reverse and scale horizontal axis

def plot_star(s, m):
    plt.plot(k*s[0], s[1], m, markersize=14-2.2*s[2])    

def join(s0, s1, m='ko'):
    plot_star(s0, m)
    plot_star(s1, m)    
        
    plt.plot([k*s0[0], k*s1[0]], [s0[1], s1[1]], 'b-')    

def draw_iau():

    join(α, η)
    join(η, τ)
    join(α, ζ)
    join(α, ϵ)
    join(ϵ, δ)
    join(δ, β)
    join(β, γ)
    join(γ, λ)
    join(λ, θ)
    join(θ, κ)
    join(κ, λ)
    join(γ, ρ)
    join(ρ, α)

def draw_rey():

    join(α, η)
    join(η, υ)
    join(υ, τ)
    
    join(α, ζ)
    join(α, ϵ)
    join(ζ, ϵ)
    
    join(ϵ, δ)
    join(δ, β)
    join(δ, μ)
    join(μ, β)
    join(β, γ)
    join(γ, λ)
    join(λ, θ)
    join(θ, κ)
    join(κ, λ)
    join(γ, ρ)
    join(ρ, ϵ)

    plot_star(μ, 'r*')
    plot_star(υ, 'r*')        
    return

draw_iau()
plt.gca().set_aspect('equal')
plt.axis('off')
plt.savefig("bootes_iau.png")
plt.close()

draw_rey()
plt.gca().set_aspect('equal')
plt.axis('off')
plt.savefig("bootes_rey.png")
plt.close()

***

[1] The diaeresis over the second ‘o’ in Boötes means the two vowels are to be pronounced separately: bo-OH-tes. You may have seen the same pattern in Laocoön or oogenesis. The latter is written without a diaresis now, but I bet authors used to write it with a diaeresis on the second ‘o’.

[2] H. A. Rey. The Stars: A New Way to See Them, Second Edition.

Suppose you wanted to write a program to plot constellations. This leads down some interesting rabbit trails.

When you look up data on stars in constellations you run into two meanings of constellation. For example, Leo is a region of the night sky containing an untold number of stars. It is also a pattern of nine particular stars connected by imaginary lines. It’s easier to find data on the former, say sorted by brightness.

Are the nine brightest stars in Leo-the-region the nine stars of Leo-the-stick-figure? Not exactly, but close.

Wikipedia has an article that list stars in each constellation region, and star charts that have constellations as stick figures. If the stars on the chart are labeled, you can cross reference them with Wikipedia.

On a particular star chart I have, the stars in Leo are labeled with their Bayer designation. Roughly speaking the Bayer designation labels the stars within a constellation with Greek letters in descending order of brightness, but there are inconsistencies. The nomenclature goes back to Johann Bayer (1572–1625) and has its flaws.

The stars in Leo, in line-drawing order, are

1. δ Leo
2. Denebola (β Leo)
3. θ Leo
4. Regulus (α Leo)
5. η Leo
6. γ Leo
7. ζ Leo
8. μ Leo
9. ε Leo

You can look up the coordinates of these stars here. Line-drawing order does not correspond to brightness order, so without a labeled star chart you’d have some research to do. My chart labels all the stars in Leo (the stick figure), but not, for example, in Virgo.

γ Leo is actually two stars, and Wikipedia ranks the brightness of the stars a little differently than Bayer did, which is understandable since brightness could not be objectively measured in his day. Wikipedia also inserts a few stars in between the stars listed above.

Here’s a plot of Leo using the data referenced above.