Hi Bernd,

I don't know the actual accuracy of the border lines; I
suspect it's variable, dependent upon the accuracy of the
maps used as sources. But it certainly ought to be in the
ballpark of one kilometer or better, not four.

Feeding those coordinates for J45 into two map servers:

http://maps.fallingrain.com/perl/map.cgi?lat=28.003&long=-15.322&scale=-5&y=480&x=500
http://mappoint.msn.com/(v4tzxsfvv2eozg55s1phfv45)/map.aspx?&C=28.003,-15.322&A=100

shows basically the same result as in Guide. So I'd tend
to suspect the MPC coordinates.

The MPC has been trying to get corrected and improved site
coordinates:

http://www.cfa.harvard.edu/iau/info/ObservatoryCodes.html

but this one appears not to have been updated.

-- Bill