Data are from the _Bright Star Catalogue_, 4th Edition, using the J2000  
coordinates.

An extinction of magnitude 6.5 is subtracted from the stars.  I used an  
extinction for aesthetic reasons because plotting the stars at their full  
brightness showed a discordantly abrupt cutoff at the magnitude limits of  
the survey.  I chose magnitude 6.5 because a histogram of the data reveals  
a drop-off in the number of stars after approximately that magnitude.   
Clearly, the survey of the dimmer magnitudes is incomplete, and I chose to  
eliminate those stars rather than give the impression that those were all  
the stars of their magnitudes.  In addition, I omitted 14 novae and  
non-stellar objects.  The resulting images show 8352 of the 9110 objects  
in the catalog.

I desaturated the colors of the dimmer stars, reflecting (in a  
non-rigorous manner) the insensitivity of our cones to dim light.

The star delta Scorpii has brightened dramatically since the BSC4 was  
published.  I fudged the datum accordingly.

Interestingly enough, proper motion makes a difference, even at this low  
resolution!  At first, I mistakenly calculated 1 year of proper motion  
instead of the 11.9 years that have elapsed since J2000.  The corrected  
JPEG of the southern polar region differed from the old by 21 bytes--not  
enough to see, but still calculable.

-- 
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