[gurps] GURPS Space star maps questions

[Scott]

1. Has anyone has ever drawn up a "real-life" star map (one with real nearby 
stars, not fictional ones). I'm planning to draw one up using Star Trek Star 
Charts (G. Mandel) as a basis.

2. How does one come up with the formula for the average distance between 
two neighboring points (1.12 × cube root of (V/N)), given the volume (V) and 
the number of points (N)? (Where does the 1.12 come from and what does it 
represent?) (ref: GURPS Space 4e, sidebar, p. 72)

3. What are the number of stars and the volumes of space covered in Space 
Atlas 3 & 4 (I've heard SA4 is double-size with 49 stars). I have SA1 & 2: 
28 & 25 stars (respectively) in a volume of 40×32×32 parsecs (Z-axis size 
assumed).