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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