Space Opera's discretionary design of planets left me wanting more
information about reasonable values for things like ecosphere and,
therefore, oribtal distance and so on.  I went looking and found
some information in a book on astronomy which I condensed down into
this table:


Spectrum	Adopted			Ecosphere
of Star		Temperature	Max	Optimum		Min
(Class)		in Kelvin		in LS
------------------------------------------------------------
B0		23,000		1072	979		876
B5		15,000		 866	790		707
A0		11,000		 742	677		606
A5		 8,600		 655	599		535
F0		 7,400		 608	555		497
F5		 6,500		 570	520		465
giant G0	 5,600		 529	483		432
giant G5	 4,700		 484	443		396
giant K5	 4,200		 458	418		374
giant M2	 3,400		 412	376		337
giant M5	 3,100		 394	359		321
N		 2,700		 360	329		294
Me(max).	 2,600		 339	310		277
Me(min).	 2,300		 287	262		235
dwarf G0	 6,000		 548	500		447
dwarf G5	 5,600		 529	483		432
dwarf K9	 5,100		 505	461		412
dwarf K5	 4,400		 469	428		383
dwarf M		 3,400		 412	376		337


The Math Used:
I did this chart many years ago, when I was in high school, so I make
no claims as to the realism of the methods used.  However, at least
they do give consistent results, so for a game they may well be good
enough.

Anyway, assume that Earth is at the optimum stellar distance around a
dG0 star.  Therefore, the Optimum Steller Ecosphere(OSE) can be calculated
as follows:
	OSE=6000K/(500LS)**2, this is simply a coefficient and is
based on the idea that the temperature of the star is proportional
to the radiation emitted and falls off as the square of the
distance.  Your mileage may vary.
	If we solve the equation, we find the OSE coefficient is .024K/LS**2

	Thus the actual Optimum Stellar Ecosphere distance in LS is the square
root of the Temperature of the star divided by the coefficient:
           __________
       _  / T/.024
        \/   

Somehow, I decided to calculate the maximum and minimum SE coefficients by
using the temperatures of dK0 and F0 stars  This gives results
of .020 and .030, which can be plugged into the above formula to
determine the maximum and minimum ecosphers.

Example:
For a type M dwarf star, with a temperature of 3,400K,
OSE = sqrt(3400/.024) = sqrt(141,666.67)=376
MxSE = sqrt(3400/.020) = sqrt(170,000) = 412
MnSE = sqrt(3400/.030) = sqrt(113,333.33) = 337