Cousin Ricky wrote:

> 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.
> 

I'm wondering how you calculated the color/brightness/size of the stars.
-- 
Ger

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